Hello, Nicole!
Congratulations on your first ever Walt Disney World Resort visit. Hooray! I hope you are having a wonderful time planning and preparing for such a magical vacation.
Unfortunately, the only Guest storage options at each of the four theme parks are in the form of lockers. While there are
various locker sizes available for rent, the largest are coin-operated ones located outside of Epcot measuring 23" x 16" x 29". Depending on the size of your child's car seat, I'm not sure they will be large enough.
As an alternative, there is taxi and even Uber service available which will provide car seats for your little one. When making a taxi request, you'll just need to specify the type of car seat you'll need them to provide. The availability is more limited, so you'll have to give yourself a little more transportation time, but it may be easier than carrying a car seat with you.
Thank you for visiting the Disney Parks Moms Panel, Nicole. We hope you have an incredible first visit and are here to help if you have any other planning questions.
Magical Wishes,
Lauren