Yes, let them talk without a head's up and encourage them to be truthful about both homes.  Chances are good that BM will bribe/manipulate/threaten/coach and get them to say what she wants. At least that's what happened in our situation.  

I told DH's lawyer to ask for a GAL to interview SS and he turned it down. He said that it never really goes well. He said that most kids will either lie and say whatever the high conflict parent wants them to say to stay out of trouble, they end up saying the complete opposite of the parent who claims the kids told them they wanted to live with them or say whatever they can so that neither parent gets in trouble. All pointless. I will say that working in the family legal field there was one exception but the girls were all older teens and they asked for a Watermeier hearing which is when the Judge interviews the kids without the parent present because they were insisting on seeing their dad more. 

Our courts use the same one consistently and ours is useless.  

The most recent case had SS14 (initially) asking to move to our house.  SS was mature and reasonable, but GAL decided--after <30 minutes with him and *no* interview with Dad--that SS was coached by Dad and shouldn't be heard by the judge.  Fortunately for SS, the judge ignored the GAL's report and heard SS anyway.  That case still took more than 2 years to finish, and it only finished because HCBM caved after reading SS's testimony (which she paid to have court reported, LOL).

Everytime that the skids have met with her, they've been clear that they want more time with Dad, and everytime, DH has ended up with more time, but it's been in spite of the GAL, not because of her, so we have very little faith.

I would not allow my children to be subjected to a GAL due to BM. It's none of my concern if skid is being interviewed.

The GAL is the only reason we have what we have. The GAL was good at listening to SS and when he would say things like "I don't want to go to my dad's" the GAL would ask why. Of course BM didn't have that part worked out well and he could never come up with anything good to say to make anyone think that DH wasn't a good dad. 

SS would say that his dad spends time with him when asked, he would say that yes, we have a nice home. Yes he gets to do fun things. Yes, he has plenty of food. 

All of BM's manipulation was outed by the GAL- but ours was a good one. 

As for prepping the kids, just tell them that nothing they tell the GAL goes back to the parents (it's not supposed to) and that they can say what is in their hearts. That both parents love them and that it is ok to tell the truth and say whatever they feel. 

Duplicate 

Kids who are kept abreast of the facts, in an age appropriate manner,  rather than allowed to be manipulated by a toxic blended family opposition parent likely have far less trouble with GAL or any other type of interview.

The quality parent, in a quality marriage, providing a quality home, providing a quality family experience, and setting a strong example of a parent, spouse, etc...  for the Skid, resident or visiting, who builds on that example with incrementally providing the kid who is manipulated by the other side of the blended family with the facts, review of specific information in the CO, in the supplemental county rules, in the state regulations, and any relevant information in play (Divorce records, arrest records, foreclosure information, legal records, repossession information, etc, etc, etc....) will come out of a GAL or any other kid interview generally smelling like a rose.  At least compared to the toxic parent who manipulates the kid and tries to influence the GAL process.

We landed on this model with my SS who was highly manipulated by the toxic SpermClan, who were hell bent on demonizing his mom and me.  Very early in the our 16+ years under the CO my SS started recognizing that "they" were behaving in ways and saying things that did not pass his smell test.  His mom and I were evil. He lived in our family all by 7wks of long distance visitation per year.  He knew they were full of shit. So, when he would return from visitation, once he got through his post visitation detox period, he would ask us a number of questions over the course of a few weeks about things they said, did, etc...  

e.g. "Mom and Dad.  Daddy-First name said he has never been married. I was looking at some of the court records and saw where he said he was married.  Why would he lie about that?"

There are potentially countless manipulations that can be minimized by keeping kids informed, showing them the documents and discussing any questions the have about the facts regularly and with increasing completeness as the kid matures.

IMHO of course.  

IMHO of course.

There is no need to prep a kid for this kind of thing if you and your SO are consistent.

It is the manipulators that have to try to prep kids and end up screwing them up even worse.

Not a GAL, but years ago BM tried to take my stepkids and move across country with someone she barely knew. Judge ordered a home study for us, BM, and the new guy. Coincidentally, we had just had a homes study done a few months prior for the adoption of our DD, so my SDs were familiar with the process and we just flat out told them, "the judge is trying to decide if it's best for you to move to ___ with your mom and so we'll be doing another home study. Just be honest with the social worker like you were for the adoption, and don't worry about anything else." That was literally the only thing we said to them on the matter, and it was consistent with what we had told them prior to the adoption home study.

We ultimately "won" in that BM was told that if she chose to move, my H would retain primary custody and she would be given a standard long distance visitation schedule. But the home study was a hot mess. When the social worker interviewed the kids at our house, there was nothing surprising - it was very consistent with the adoption home study, which had been glowing and obviously recommended finalizing the adoption.

But when she interviewed the kids at BM's home and and the new guy's home, and asked the exact same questions, the responses were drastically different and quite frankly shocking to us. It was very, very hurtful. The kids said that they were scared of us, they didn't feel comfortable in our home, they felt that H had abandonded them and that he only cared about DD, they wanted to only see us during the Summer, didn't feel close to my in-laws, etc etc.

The social worker wrote in her report that she felt it was very obvious that BM had coached the kids on what to say and that we had not coached them. Her reasoning for this was that at BM's and the new guy's homes, both kids used verbatim the same phrases even though they're two years apart in age and were interviewed separately. And that their vocabulary wasn't reflective of their ages or intellectual development, nor was it consistent with the way they spoke when she interviewed them at our home, or in conversations when she was just observing their interactions with other people. 

We were really thankful that she was perceptive enough to notice and explain all this in detail in the report, but I will say that when we ended up at trial and she was on the stand, she COMPLETELY froze and didn't relay any of this in a convincing way. I'm not sure if saying it out loud in front of BM scared her or what, but our attorney had a hell of a time getting her to directly answer any questions about coaching. Fortunately we had a good judge who had actually taken the time to read the report. If she'd just based it off the social worker's actual testimony, it wouldn't have been good news for us. 

All in all, I feel like we handled it appropriately by not trying to prep them at all and if I was ever in the situation again (I won't be, because I'm d-o-n-e with dealing with stephell), I would do it the exact same way. That being said, knowing that we didn the right thing didn't make it any less infuriating knowing that BM was trying to cheat the system and didn't truly suffer any consequences for it.