I understand it's not what OP is necessarily pushing for.. but it does seem like a recipe for disaster to take a disgruntled teen (and most are disgruntled to some extent..lol) on a trip where you are in close quarters.  But this kid is dang near estranged from his dad right not.

1.  The cruise is kind of a reward type of activity and I would be danged if money would be spent taking an ungrateful snot on a trip.

2.  Danged if I would subject the rest of the family to the risk that SS would melt down at some point on the trip and ruin everyone else's time.. ie MORE money down the drain.

I think her DH needs to let the trip go.. it is too high stakes.  If the kid won't even TALK to him directly in person.. how on earth does he think he can logistically manage dealing with him on a complicated situation like a cruise vacation.  I mean, the kid literally might do something stupid.. jump off the boat.. push someone off the boat... run off at a port.  So many disaster scenarios..

I understand that her DH wants to see his son.. and I guess he is hoping that this great golden goose egg of a cruise will be enough to mollify his little boy into having some relationship with him.  Disney daddying to the fullest.  You act like an ahole.. I will buy you a pony.  I mean.. what's next.. dad buys him a new car when he is 16.. so the kid will deign to  talk to him?

He is trying in some ways to buy the kid's love.  I do NOT think he should give up on the kid.. but I think the efforts to get him on this trip are probably going to end up a problem.

I have followed this entire situation for a long time now. . OP husband has been on float, it is OP who has been driving much of this train. Even before they were married.  Cant believe dh's lawyer has given op the time of day.   The parties in the court proceedings are Dh and bm, not dh, op and bm. There is limited info dh's lawyer is allowed to discuss with OP. 

OP during DH's 'deployment"  can call dh's lawyer all day long, every day, BUT unless the attorney hears it directly from DH the attorney cant use it.  So what OP is doing is double dipping attornies fees...OP calls lawyer tick tock tick tock $$$$$,,then attorney must back track with dh and charge again.

 Same thing with medical doctors..OP can call and call and call thinking she will be able to gain access with staff. They should and are required to not speak with her about dh's and BM's son.  Especially since this boy in particular is not in the custody of DH. BM has physical and dh is ncp. DH should have full access to kids medical.

OP's GAL should not give OP one single hint about what he is doing. UNLESS he is assisting in a minor minor conflict. GAL can be kicked off the case for that.

What is ok would be:  "Ok dh, I will call bm and see what we can do about returning your winter coat back". GAL should not be so involved with OP...

I think if dad could show the umpteenth times he has tried to exercise visitation that have been rebuffed.. the umteenth times he has tried to get an answer from the boy and his mother as to whether he will go on this trip.  The repeated messages from "the boy" (might be bm I guess they can't tell).. saying he is not going.

I'm not saying he should give up on the boy.. but I think a judge would see his attempts and say.. look BM/SS.. he tried a hundred times to get you to go.. don't be mad about that.

I mean.. that may not be how it would go.. but it seems likely that someone would see his repeated attempts to have his custody time rebuffed.. and refusal to cooperate with these plans as alienation on her part.

I actually just think it's a horrible idea to take someone on a cruise that will not speak or respond to you.  It's patently unsafe.  If he is really "all in" on getting his son back in his life.. I would cancel the cruise and just try to get the kid to come to him for counseling etc...