Hi Shawna!!
I am so excited for your four year old son and his first trip to the Walt Disney World Resort!! I have a three and a half year old and know the excitement and joy that your son will be experiencing!!
There is such a great variety of Character Dining options that are available for you on your upcoming trip!! A guest favorite is
Chef Mickey's at Disney's Contemporary Resort. Chef Mickey's offers breakfast, lunch, and dinner (all are buffet) and is very accessible from the Magic Kingdom!
A personal favorite of my family is
Chip 'n Dale's Harvest Feast at The Garden Grill, which is located in the Land Pavilion at Epcot. This Character Dining option offers a very unique experience in a revolving restaurant at Epcot. This meal is served family style with the various food offerings being brought to your table. Chip 'n Dale's Harvest Feast is only offered at dinner time.
As far as Cinderella's Royal Table is concerned, I think your 4 year old son would love it. The boys often times get some great attention from the Princesses, which makes it such an awesome and memorable experience for any child! I would definitely book this at 180 days out as it does book up very quickly!
Have a magical trip!!
Scott