Hi Lauren,
Your first time at Walt Disney World with your son will be so magical! Like you, I had traveled to Walt Disney World many times as an adult before my child was born. Traveling with your little one allows you to see the pixie dust from a whole new point of view!
I am glad that you are already aware of
Rider Switch, which is designed to allow you to experience attractions at Walt Disney World that your baby cannot or does not want to experience. Rider Switch allows one adult to ride the attraction while another watches the baby, and then you switch who is watching the baby, and the adult who initially watched the baby can experience the attraction without needing to go through the whole queue.
As for your baby, he will be able to experience many of the attractions at Walt Disney World! Essentially, as long as there is not a height requirement for the attraction and you are comfortable with him going on it, he can go on it! There is a list of
attractions with height requirements on the Disney Parks Blog. This blog post lists the attractions with height requirements at Magic Kingdom, and there are links to height requirement charts for Epcot, Disney's Hollywood Studios and Disney's Animal Kingdom Park. In the upper right-hand area of each attraction page you can also see if there is a height requirement to ride. For example,
Soarin' at Epcot has a height requirement of 40 inches, whereas
it's a small world allows guests that are any height.
Please do let us know if you have any further questions, Lauren!