We went in 04 during Spring Break and it was CROWDED! But if you get there early, use FP a lot, take afternoon breaks (especially because you're staying at the DLH = easy access to monorail = easier breaks), and stay later, you should be fine.
Just to give you an approx., lines for major attractions in the morning should be no longer than 30 minutes, but by midday, rides like Space, Indy, and Splash will be up in the 45-60 minute range. Nemo will be long starting early, so hit that first. Fantasyland rides are good to hit during EE (which you have every day that it's offered during your trip because you're staying onsite), as is Nemo if you have more than one EE day. DCA's rides open at 10 (9:30 for Soarin) and won't have long lines until at least noon.
As for weather, it's very nice. Warm, not muggy, and sunny. There might be some little showers, but nothing large at all.