No. She could always call it stolen and that would really ruin the trip.

Wouldn't bother me. Wouldn't want the headache that could potentially come from HCBM

Not to mention if something should happen, like a minor fender bender or even a scratch of some kind, I think, depending on the insurance policy, if a person not named on the policy was driving the insurance company can decline to pay or BM could make a big stink over it.

I wouldn't risk it myself.

I wouldn't have an issue with it because it's in BM's name. The only concern I would have would be regarding insurance and being sure that SO is covered when driving someone else's car if something should happen.

Without knowing the full story, how would BM know that SO is driving it if it is SO and SS on an trip?
If it is that big of a deal, then I'd say it makes more sense in the long run to take SO's vehicle and save the headache, otherwise I'd say, not a hill worth dying on.

Ugh... I feel like what you are really getting at is something many of us struggle with; SO of DH level of connection to the BM. I am at the point after 13 years that ANYTHING even remotely connected to the BM means trouble. However, there are things our of our control. You cannot set rules for stuff like that especially if you are not part of the activity. Lots of these men walk into things blindly because they want to be with their kids and also not look uncool. The best thing I've done is ask less, discuss less, know less. BM is not significant to me and I'm done with monitoring my DHs actions. If it directly concerns me then I have a voice.

It wouldn't be worth the risk to me.