While I hope for the best for you and your travels, I also have great empathy and understanding! I know all too well what you've described. SIL and BIL pull the "whatever you do is fine!" line with us every time. And we have tried to politely set them up on a separate adventure... once, right before Hurricane Charley came ashore, we "ditched" them in the hotel that morning. They did just fine - they had a late morning and leisurely b'fast on their own while our crew did EPCOT. But I still ended up taking an extra 3 days on our trip just for some private family time. And it really does depend on the company you keep - because when my sister and her family travel with us, we NEVER have that problem. We go our own ways, meet up for dinner - it all works well. On our last 2 trips, we didn't extend the invitation to SIL/BIL because as you described, our dd and their ds didn't click too well at all. Our parenting styles are very different too. Well, imagine my surprise when she turns to me this summer and says, "Hey, BTW, we decided we're coming with you on your Disney trip next summer." What the poooo?
I informed them it likely wouldn't work out - we can only travel the first 2 wks of June next summer, and that's 2 weeks too early for them and their school schedule. Not a problem, she says - their son will just miss school. What the double poooo?
The last 2 weeks of school? THe field trips, final tests, all that? She also didn't understand why it would be a problem for them to stay with us (we have a fam of five and intend to use the WHOLE 2 br villa, no, you can't fit 5 more folks in there with us!) They are amenable to getting their "own" villa but very adamant on staying in the SAME type place as us. Ok, fine, sez I, and I showed BIL a little spreadsheet I worked up, showing him the cost of the 1BR villa, and also the cost of a 150 pt HHI resale. He says, "But we don't want to go to WDW every year. I said, "And you probably can't - not with only 150 pts. But you could bank and save and do WDW every other year for at least a week, you could even do HHI which SIL loves every other other year... you could work it out that you do WDW every 4 yrs, and HHI every 4 years, or something like that.... He looks at the table and says nah,we will just pay cash for the room. He then later tells DH that it would be "stupid" to buy into DVC - that he would do better to just invest his money. Well, you can call my poor DH a lot of things, but when you accuse him of being careless with his moolah - them's fightin' words.
I get stuck doing ALL the planning, then, as we cruise around WDW I have to hear my BIL make fun of all the expenses, when I have busted my patookus to get the best deals out there for them. No one so much as cracks open a map, - they expect me to do it for them, then they get to make fun of me and my "obsessive-crazy planning." Grrr. So I'm having a REAL hard time getting worked up about this trip. I have reserved a room for our fam, but nothing for them. Haven't looked into tickets, or anything of thae sort, even knwing that the tix prices were rising a few weeks back. It's hard to work up even a modicum of energy.
I do agree with the posters who have said sometimes, however, a change in travel ways (like not planning when you normally obsessively plan) can be a nice switch and pleasant surprise. Last year we went to Universal and Disney sans any family, and I really didn't do much homework at all. It was a great trip, and fun was had by all. Maybe that's another reason for my current apathy - I'm beginning to learn that fun can occur spontaneously too.
In any case - I hope your trip is a great, relaxing and fun-filled surprise as well - no matter who is along for the ride! And if you don't FEEL like planning -hey, go with that. Maybe it's an idea whose time has come!!