Deanna:
Usually I'd say that travel in May, except for the weekends, is manageable, until Memorial Day. However, Memorial Day comes early this year--at the end of the third week of May, so the crowds will be higher in anticipation of the weekend.
One of my favorite sites for crowd forecasting is
www.touringplans.com and it confirms that crowds will be thicker that week, and on a scale of 1 to 10, close to a 9 by Thursday. However, if you visit the small parks like Magic Kingdom and Disney Studios earlier in the week and leave Epcot, the largest of the parks, for the more crowded days when its expanse can handle the crowds better, you can make it work!
Wishing you a magical vacation!
Whitney