Lexie, thanks for your words--I sometimes still forget that I don't have to overexplain myself to him. Less is often better. I still find myself needing to justify at times or explain as if he'll understand his kids' feelings.
Talked to both boys last night and reminded them of the language in the plan. DS14 says he will NOT go. He also said if Dad gets angry and decides not to come here (to punish them, as he's done historically), that would be great. He doesn't need to see him or get a gift.
DS16 said he's not going if DS14 doesn't go.
I told them I would send Dad an email, and that I'd include a request that in the future he checks with me before booking things.
Haven't had the energy to draft that yet. Lol. I'm making it harder than it needs to be.