It's going to be crowded (but not as bad as later in the month) no matter where you go for the day. Just adjust your expectations/attitude and you'll still have a wonderful time.
Personally, I'd go to MGM, and make good use of the FastPass system. If the crowds were "more than I could stand", I'd try to visit the attractions that have high capacities such as the Beauty & the Beast Show, Indiana Jones, etc. I'd plan a sit down meal (with PS) for the busiest time and try to do things that others may "overlook". I'd go in knowing I'll probably have to wait 60 -90 minutes to get a decent seat for Fantasmic and plan to eat my dinner in the stadium. Etc.
It probably won't be as bad as you fear - it's all about expectations. Crowds are just part of the experience - if there weren't crowds, Disney wouldn't exist as it does. If you know and expect crowds, it won't bother you so much!
Best wishes -
