Howdy Alison! I'm so excited for you!! You and your daughters are going to have a magical time at the Walt Disney World Resort!
For a wonderful dining experience that doesn't require a reservation, I would suggest that you visit
Be Our Guest Restaurant for a delicious quick-service lunch. It's truly magical! You will dine inside of Beast's enchanted castle. The ballroom is breathtaking and the food is yummy! My favorites include the French Onion Soup and the Triple Chocolate Cupcake!
If you decide you want to visit Be Our Guest for lunch, I would suggest that you plan to get in line early. As one of the newest restaurants on property, it is wildly popular and will fill up quickly. Your girls will love the experience!
Other than that, I want to encourage you to visit New Fantasyland and the classic attractions such as "It's a Small World" and Dumbo the Flying Elephant.
There are so many amazing attractions to experience while you are there. I have named just a few at Magic Kingdom. If you would like suggestions for some of the other theme parks, please let me know.
Thanks for your question and have a magical Spring Break at Walt Disney World!