Thanks. everyone! I think we'll have two plans, and then play it by ear which one we follow. It's good to know that the break has worked out well for some.
We'll be there in mid-September, so hot but nothing we're not used to here in Texas. I think closing time is scheduled for 9. *Typically,* my girls are good to be out and about as long as we need to, but once we head home we usually stay home. I don't typically take them out more than once a day (our drive into 'town' from home is about as long as the bus ride from MK to AoA, I suppose). I know we'll be at the park at rope drop, because my girls hate to sleep past 5 am.

Ideally, we'd be able to take the break after lunch, go back for an early dinner and another ride or two, then I'd take the little one 'home' for bed while DH kept the big one at the park for fireworks... but realistically, we're early-to-bed types and the kids need a slower evening. I'm pretty sure that if we headed back to the resort for naps, we'd never make it back. (Especially since we don't have park hopper passes or anything).
So I guess it's best to let the momentum of excitement carry us as far as we get, and then be done whenever we're done... whether that's noon or 4. Then dinner at the resort and evening pool time. I'm sure we'll make our way back to WDW when they're older. They can see fireworks then.

I have to keep reminding myself... even if we do nothing but ride our 3 fast pass rides, eat a Mickey Bar, and use every restroom in the park three times, it will be magical.