Janet!
First of all, I am TOTALLY going to be there at the same time! Moms Panel reunion from the 27th through the 29th, then back with my family starting the 2nd! So if you see me, you BETTER say hi!
If those grand kids are at all like my two girls, I would go to the
Mickey's Not So Scary Halloween Party on your last Friday, the 4th. Here are a few reasons why;
Get me to the beach on time! My kids love the beach, and even on their Disney Cruise they could not wait to get to the beach. Don't shorten their day by having them out late the night before.
The Grand Finale. Can you imagine a better climax to a vacation than your entire family staying in the Magic Kingdom until late in the night at a special event party? Shorter lines, extra fun, late hours? Who could say no to that?
Snooze before you zoom. Let them sleep in on the 5th and instead of going to a park, just go hit the resort pool. This is a good way to wind down the vacation and give yourselves plenty of time to pack for the flight home. Maybe throw in a character breakfast at a resort at the latest time available, and you get a really nice, slower paced send off on your final day.
Just my opinion. Either would be fine, but this is the way I would do it. Write me back with more questions!
Have a magical vacation!