Hi Vanessa!
Your 4 year old is going to LOVE Disney! There's so much magic for a 4 year old child to enjoy, I don't even know where to begin! There are lots of exciting shows like Playhouse Disney - Live on Stage at Hollywood Studios, wonderful attractions like the Seas with Nemo & Friends, there are character Meet-n'-Greets where your child can get a picture or an autograph with his favorite character and so much more to enjoy. At 4 years old, your child will have no problem riding attractions that don't have height requirements. If you want to enjoy attractions that your 4 year old cannot ride, you might want to take advantage of the Rider Swap option, so you can take turns with another adult waiting without having to stand in line twice.
When we travel, there are two things we pay lots of attention to in order to keep our 3 year old happy: naps and snacks. My kids don't have a problem with napping in their stroller, but sometimes we go back to the resort to rest a bit in the afternoon and go right back after a short nap. The snacks and water bottles are always great because when meal time is a bit later than expected, the snacks keep the kids happy. For great information about traveling with small children, check out the
Traveling with Little Ones section of the WDW website. So start planning your Disney vacation because 4 years old is a great age to visit.
Have a magical vacation!