Hi Brooks! What an incredible experience you will have coming to Walt Disney World for the very first time with your four year old.
I realize that the park tickets seem pricey but you do get so much once you are in the parks. All of the parades and fireworks shows and all entertainment is included in your admission. And of course all of the attractions and character meet and greets are included as well. Food and souvenirs are extra so you can budget knowing that and decide what kind of meals and restaurants you wish to visit.
Most guests will head to the
Magic Kingdom Park for their first visit. It is truly the park that emits that magic all guests expect when they hear the word Disney. However, there are more then 30 different things to do from attractions and characters and such and to do it in one day is not only hard but also exhausting. I always suggest guests head to this park at least for a two day visit.
On top of the Magic Kingdom, Walt Disney World also offers three other parks: Hollywood Studios, Animal Kingdom, and Epcot. All three of these parks are amazing and offer younger children fun things to do and experience. If you wanted to visit all four Disney parks it would be at least a four day park ticket. So to say you can do it all in one day is pretty near impossible.
I suggest you read about the various parks and what is offered and then decide if you can budget for more then one day at Disney. Perhaps on this trip you will just want to enjoy the Magic Kingdom Park and head there two different days. Your choice will likely depend on your budget but no matter what you decide I am sure you and your four year old will have a trip of a lifetime!