Hopping in from Florida....
WOW, it's amazing the mixed review on this. But down here, it is awesome to go with friends. Especially if the kids get along great. And want to do stuff together, you could take turns babysitting. Plus there's the sandcastle club that's offered in the evening for out of diaper age kids - 12yrs old. That way the kids will be on thier own, and you parents can do your own thing.
I think a lot of you guys have a misconception of how much there is to do, and how easily you can split up. You don't even have to do dinner together, maybe just breakfast at the resort, or in your room.
Plus I don't know how this worked, but I was talking with disney about getting two rooms at Port Orleans French Quarters, and the second room would be discounted to like half off. So it's not like you're gonna be up together, eating together, and everything else together.
And so what if you make plans to meet (unless it's swapping kids or something) if the others don't show up. You could be there for 2 weeks and not get to do everything.
It's probably a major help if you are driving. And when you're on a road trip, no one likes getting up early/late, sitting in the car for 10 hours, eating at stupid road-side places. Every one suffers through those. I hated my g'parents when we would leave for trips to Indiana, they would wake me up at like 3 or 4 am before the sun would rise, and I just slept for the next few hours. Any other day after that, I think we were up at about 7am. But no matter what, we stopped in whatever city/town at dinner time, found some place to eat, then found a hotel, and if there was any time, see if there was anything cool to see in town before going to bed.
You can always get one of those big ice chests to put in the van and fill with drinks and snacks. You know what your kids like, they know what their kids like. And at night, just borrow some ice from the ice machine at the hotel. Or buy a bag at 7/11 for a buck.
If I could go back to when I was younger, and plan a Disney trip with friends, that would be so cool. And if you split expensis, you just might end up with some extra money for souveniers, and who doesn't like lugging around a big mickey, with a pair of ears on, and a pin trading lanard around your neck, and wearing the coolest disney shirt that's probably 2 sizes too big.
Each family can make thier own iteneraries and if you plan to do things like the specialty cruises, just make sure you both agree on the day. But if you do want like group photos in front of the castle, just get it all over with in the first day. And if you get the park hopper, you can just leave and do something else at another park without worries of bumping into each other.