Hi. Just got back from WDW yesterday. On Sun 4/25 at MGM studios, the place seemed empty to me. We strolled around, never waiting for anything, even to meet characters. Great weather too. Mid-80's and sunny.
Mon 4/26 at MK, crowds were definitely bigger than at MGM, but not too bad at all. Since our kids are 5, 3 and 5 mos., we were not trying to do Space Mtn or other big kid/adult rides. But our longest wait of the whole day was 10 minutes, for Dumbo. We followed the "Touring Plan for Small Children" that is linked on the DIS and it was awesome. We walked on to most rides and used fastpass wisely. I felt a bit guilty about walking by all of those standby folks on Winnie the Pooh, Buzz, etc. but they could have used FP too, I suppose. I don't understand why more people don't use it. We got to see every one of our must-sees by mid-day, and the rest was just gravy. Weather there on 4/26 was hot and humid. 87 degrees and 90% humidity. Hey, what're ya gonna do?
Tuesday morning at AK, I was surprised at the number of people hightailing it over to KS. Still the wait was onlly about 10 minutes, if not less. Then Lion King Show: we had to wait until the showtime, but that is to be expected. Weather Tuesday was a bit cooler and there was a lunchtime rain. We managed to get into the Rainforest Cafe before the skies opened. By the time we finished lunch, the rain had stopped and it had definitely cooled off nicely. Went back to MK in afternoon and found crowds to be moderate and manageable. Of course, we left just before the 8:30pm parade (to get the kids to bed) so I can't tell you what the crowds were like leaving the park at closing.
Don't worry about crowds this week. Figure out what you don't want to miss, make sure to use Fastpass whenever possible, and you'll have a great time!