I don't know the exact dates, but I would guess the weekend closest to Veteran's Day. We went that weekend a couple of years ago, and were surprised to find out about it.
It was extremely crowded at MGM that weekend, but not as bad on the rides. Navigating through the crowds was annoying, but most people just wanted to meet the stars, so the lines weren't too bad in the middle of the day, considering how many people there were.
EPCOT and AK were quiet compared to the huge crowds at MGM. MK was ok on Friday, but an absolute zoo (as usual) on Saturday. We couldn't even walk together at MK - just in a line hanging on to a kid's hand for dear life. We left the park that day.
Getting PS for meals was hard because apparently the hotels were full. Even though we didn't see a lot of people most of the time, everyone had to eat dinner. We made our PS way in advance, so it didn't cause a problem for us, but I did hear a number of conversations about it while waiting to be seated.
We still had a great time, but I don't know if I would go that weekend again. I'm sure you would have a good time - after all it's WDW!!