We've gone pres week many times and the crowds are usually 8s then. The time you've got 7s, 6s, 5s, and 4s! You should be fine. We are going 4/13-21 and 7s are predicted most of the time.
If you haven't already, buy the Touring plan for $8.95 and follow the suggested recommendations for the parks, which to avoid, which to go to and even which rides to do when.
Don't despair! The weather will be so nice and you're at Disney!