Hi Christina! You will be staying in my absolute favorite Disney resort, the
Fort Wilderness Campgrounds. We just love the ambience and quiet this resort brings to us after busy days in the parks. It feels like we are in a completely different place then at Walt Disney World. But it comes with all the perks and amenities of all the other Disney resorts so you are getting the best of both.
You will basically have two options for full fledged spas on Disney property. The
Senses Spas are the highlighted places to go for a full complete spa treatment while at Walt Disney World. There is one at the Grand Floridian Resort and one at Saratoga Springs Resort. The closest of the two is probably Saratoga Springs. You would need to drive a car, take a taxi, or hop on the bus to Disney Springs and then connect to Saratoga Springs from there. For the Grand Floridian Spa you could drive, take a taxi, or hop on the boat to the Magic Kingdom and then transfer to the monorail to get to the spa. Both will take time so budget that in your plans.
You might also consider simply heading over to the Yacht and Beach Club where they will only do massages and facials. This is a small facility but still very nice. You just won't get the ambience and ability to enjoy a spa experience there.