We did a "couples" trip to WDW with my parents, a couple of years after my sister and I were each married. We did stay in the same resort, but my sister and her husband opted to stay in a different section than my parents and DH/me. We knew going into it that nobody expected us to do everything together, all the time, and we all committed to not taking it personally if anybody wanted to go off and do their own thing. Instead, we sat down before the trip, planned one daily table service dinner that we were all going to do together -- plus MK together on our arrival day and fireworks together on our last night -- and left the rest up to more last-minute planning. (Granted, this was in the days before you had to book Fastpasses ahead of time, so we didn't even have to decide on parks beforehand: we could just decide the night before what we thought we wanted to do the next morning, and see if anyone else in the group wanted to come, too.)
It worked out beautifully. Everybody could be as together -- or as separate -- as they wanted. My parents tended to sleep in while my sister and I and our husbands rope-dropped a park together, so they'd just call us mid-morning if they wanted to find out where we were and join us. My sister and her husband liked to reserve their afternoons to themselves, so DH and I would make our own plans, or just pal around with Mom and Dad. Regardless, we could all look forward to meeting up for a relaxing dinner together every night and swapping stories about how we'd spent the day, and while we were at it, we could discuss whether anyone wanted to make group plans for that evening. (In fact, I do think we ended up sticking together most evenings after dinner.)
We didn't spend a lot of time hanging around the hotel, so the fact that we were at the same one didn't affect our experience very much (although I did love being able to pop over, snuggle up with my Mom and kibitz with her at bedtime, like I was a kid again: their room connected with ours, at our request). To get together from distant ends of WDW, we just called (yes, this trip was even pre-texting capabilities, now it's so much easier!) and met each other in a park or at a restaurant.
My suggestion is just to have a pre-trip family meeting (preferably before the 6-month ADR window opens, if that's possible) to set expectations and decide on a few things (whether it's meals, FP attractions, shows, etc.) that you know you want to do together. The rest of the itinerary can be left flexible, so that everybody has sufficient breathing room if they want it, but can join up with others if they find they don't.