I'd go any day of the week any month because it's my favorite park!
Seriously though I think you'll be fine. Epcot is so large I never seem to feel really crowded there,except for one time.The very first Friday of the Food and Wine Fest. a couple years ago...OY! It was a madhouse that evening but we still had fun!
We were there 2 weeks ago on a Saturday and it wasn't bad at all. Either Sat. or Sun. sounds like a good day to me!
Thanks Baloo. My family is spoiled and depend on me to sorta have a rough schedule for each day. The clock is counting down and our schedule and PSs are still not hammered out. Yikes!