Hi Jen,
Welcome to the Disney Parks Moms Panel! After consulting with my 6-year-old son, we agree that your 4-year-old would enjoy one day at Magic Kingdom and one day at Disney's Hollywood Studios best. My son was two when we took him to Walt Disney World for the first time. He's since been back every year, and I can recall his visit to Hollywood Studios at the age of four. He loved playing at
Honey, I Shrunk the Kids Movie Set Adventure and seeing his favorite Disney Junior characters at
Disney Junior - Live on Stage! was a magical moment we’ll never forget. Another family favorite is Muppet*Vision 3D. We always enjoy the spectacular 3D presentation and leave smiling.
The Magic Kingdom is my favorite park in the Walt Disney World Resort to visit with my kids. With the recent expansion of
New Fantasyland, Magic Kingdom Park has more to offer than ever before. My kids enjoy traveling through the Hundred Acre Wood with Winnie the Pooh and friends on The Many Adventures of Winnie the Pooh.
Casey Jr. Splash 'N' Soak Station in Storybook Circus is great space to cool off and get out some energy. Depending on your budget, I would suggest adding on the Park Hopper option. This would allow you to "hop" between the parks, in case you need a change of pace or missed an attraction at the park the previous day.
Please feel free to send me any follow-up questions as you continue planning your spring vacation to the Walt Disney World Resort.
Have a magical day,
Bob