Hi Jaime! My family's probably visited Walt Disney World in May more than any other month. I love the comfortable warm weather then and the fact that the crowds are quite manageable since most children are still in school. Attendance levels in the parks will probably be slightly lower the first week of May than they would be later in the month. You'll usually experience low to moderate crowds in May, but attendance levels do climb a tad as the month goes by and colleges and schools begin releasing students for summer vacation. Also, Hollywood Studios begins hosting Star Wars weekends in the last week or two of May which can bring in the crowds. As a general rule, park attendance is a little higher on the weekends than during the week since many local residents visit Disney World on the weekends. For this reason, you might find the crowds to be lighter during your Tuesday to Tuesday visit during the first week of May.
Hope your second trip is magical! Come visit us again at the Moms Panel if you have more questions! We'd love to help!