Hi Lindsey,
It sounds like you are planning a fun birthday celebration for your little guy! Disney World is the most magical place on earth to celebrate your special occasion.
As far as which resort to stay in, the fact that you have five adults will be a factor in that decision. Unless you plan on staying in a Disney Vacation Club resort (condo), you will want to book two rooms. Depending on your budget, I recommend at least a
Moderate Resort as they have queen sized beds. The Value Resorts have double (full) sized beds which can be a tight fit for two adults. My favorite Moderate Resort is Port Orleans French Quarter. It has a calming atmosphere and is much less spread out than Port Orleans Riverside, the Caribbean Beach Resort and Coronado Springs Resort.
Breakfast at the Tusker House is a great idea. Donald, Daisy, Mickey and Goofy are decked out in their safari gear and it is a lot of fun. I highly recommend the Crystal Palace for breakfast. Your birthday boy will see Winnie-the-Pooh, Tigger, Eeyore and Piglet. The character interaction is always fantastic there and the food is delicious. You might want to try Chef Mickey's as well for the "Fab 5" (Mickey, Minnie, Goofy, Donald and Pluto) in their traditional clothes.
I hope this helps. Please do not hesitate to send a follow up question if I can assist you further.
Wishing you a wonderful vacation,
Kaylene