FiveOh,
I expect any day during Spring Break can get crowded at the Magic Kingdom. I live in Orlando, and I feel I can go to the Magic Kingdom any day. The secret is to arrive early, before the Official Opening Time, on a non early-entry day. If the park gets too crowded later in the morning, I use Fastpass to my advantage and concentrate on the live shows and parades (arrive early to get good spots). If your kids like characters, line up early for any character meet and greet. For example, Mickey's Toontown Fair usually opens one hour after the park opens, so you can line up early to meet Mickey in the Judge's Tent and then other characters in the Toontown Hall of Fame Tent. If the crowds get oppressive, I head to another park or get on the monorail and explore the monorail hotels. The Water Mouse Boats available for rent at the marinas are a big hit with kids.
Steven Barrett, author of the "Hassle-Free Walt Disney World Vacation" and "Hidden Mickeys, A Field Guide to Walt Disney World's Best Kept Secrets", both books published by The Intrepid Traveler Publishers