We were in Orlando May 29-June14 this summer. We focused on WDW June 8-14, so that is about the same time you are planning on going.
The crowds were moderate. We got to the parks early (only like to do EMH at MK to get Fantasyland done during that time) and took advantage of Fast Pass and leaving in the afternoons for breaks and we handled it great.
The hardest thing for me, personally, was the heat. We decided to stay at Epcot one afternoon and not take a break; it was unbearable. Won't do that again without taking a breat at the resort to cool off. The heat was INTENSE!
We do late May/early June now all the time so we don't take our kids out of school any more and that time is fine.
Really make sure you keep the water going on your kiddos. My 5 year old DD got very ill at IOA one day. The heat was intense and we obviously did not push the fluids like we should have and she suffered from heat exhaustion. She became quite lethargic in the evening back at the villa and started vomiting. Needless to say, we were quite worried about her, but she got some gatorade slushes to stay down and she got better.
Go and have fun!