chEARs Jenni and Happy Un-birthday to you! My mom always said that MY birthday was HER birthday (since it was so special), and I'm sure you feel the same way about celebrating your little guy! I have four-year-old twin boys, so they're going to help us plan his birthday celebration!
First, where to stay? It sounds like you are interested in Disney's Fort Wilderness Resort, and my boys agree it is fantastic for the littles! I can't tell if you are planning on bringing camping equipment with you, but if you are, the Campsites are great. The sites have cable and electrical hook-ups, a charcoal grill and even a picnic table! If you aren't bringing a tent or an RV, but still want a rustic adventure, I suggest the Cabins at Disney's Fort Wilderness Resort. They have a living room, full bedroom and bathroom, patio (again with a grill!), and kitchen in each of the hideaways.
While you are at the Resort, take your little guy to the stables at Tri-Circle-D Ranch. There the birthday boy can meet Shetland ponies, Clydesdales and more! He can also giddy up for a pony ride on one of his new friends!
Speaking of new friends, Lightning McQueen and Fancy Nancy are now at Disney's Hollywood Studios. Disney Jr. is HUGE in our house, and I am sure your son would love to meet some favorite Disney Pals! We just returned from a trip to Walt Disney World and had a blast at the brand new Lightning McQueen's Racing Academy, and Disney Junior Play 'n Dine at Hollywood & Vine is THE place to go to greet a bunch of Pals at once (including Vampirina and Roadster Racer Goofy)!
One of the benefits of staying at a Walt Disney World Resort Hotel is the complimentary Extra Magic Hours. These happen before or after regular Park Hours and are exclusive to Resort guests. You can check for Extra Magic Hours online, on the My Disney Experience app, or when you arrive at your hotel. Extra Magic Hours require valid Theme Park admission and depending on how long you are visiting; I am sure there is a combination that will work for you. To explore your options, head here.
Jenni, my boys and I hope this helps you plan your magical celebration! If you have any other questions, please don't hesitate to come back.
Rayna