Party of 8 or 3+5 or 4+4?

[eeyore29]

For our upcoming December trip, some friends might join us and I'm not sure how to go about the dining & BBB reservations.

My family: DH, DD4, and me (this will be our 9th trip).
Friend's family: husband, wife, DD5, DD13 (all first-timers).
And a single female friend who went one time as a kid 20+ years ago.

So if everybody goes, that makes 8 of us. Everyone has made hotel reservations for POP. We have already told them that we might upgrade if we meet some personal goals (they won't be upgrading with us). Every time we've gone to WDW, these friends have said "yeah, we'll go" until it came time to actually book; they've backed out for various reasons. The fact that they've already booked their rooms doesn't make me believe that they're actually going this time either, since they can still cancel & get a refund for several months yet. Call me pessimistic, but these friends have backed out on a lot of things over the years; this is why I'm hesitant about making dining reservations.

The last few years, other friends have gone at the same time as us, and we've met up for a day or a meal or two. That's what we like. I don't want to feel like I'm stuck with people for a whole week straight. Heck, I grow tired of DH after a week straight! We have different opinions on what a vacation should be: he wants to go-go-go & do as much as possible, whereas I like to relax & take it easy. We've already said something like this to the friends, so they know how we feel...but then they've both said "we'll just do what you guys do."

So here's where I'm looking for suggestions:
How do I reinforce the "time together & time apart" without offending anyone?
Do I make the dining reservations for 8? Or just do mine & let them do their own? I know we won't get to sit together if we book separately, but then that might be good for a few reasons: they have their own time with characters, we'd probably each get seated quicker than waiting for a table for 8, plus won't there be an automatic gratuity applied for a party of 8? And most of all, if they cancel, it's not MY job to call & change everything.
Another issue is, who gets the single girl? Take turns with her?

 

[parkhopping]

Based on what you've said, if I were in your position...

-I would make one dinner reservation for the trip for all 8 of you. That way, if they do go, you know you'll have this one time for all of you to be together. If they cancel, it's only one reservation to change.
-For the other reservations, split up. This is the only reasonable thing to do given your friends' tendency to cancel on you. When you check in at the restaurant, you can explain that you're all together and ask if it would be possible for them to seat you near each other. If they can do this, great; if not, no sweat. If your friends find this odd, you can explain that it's easier to make reservations for smaller groups than larger ones (which is true). As for your single friend, I would just ask her what she would prefer to do when you need to split up. Don't forget that the younger kids may want to sit together sometimes, so you may need to do some reshuffling.
-As for "time together & time apart"...I would just explain to your friends that while you are looking forward to vacationing with them, you'd also like to spend some time with just your family. Perhaps you can agree on certain attractions you'd like to do together, or plan to spend the morning together and have lunch, then split up after that. Just be sure expectations are clear ahead of time.