Hi Bonita!
You are referring to the Race Retreat tent. You can find more information about it on the
Disney World marathon weekend website. Click on "EVENTS", and then Race Retreat.
I have used the race retreat many times for different races. If you can afford it, I definitely think it's worth the money. It can be pretty cold on race morning and this tent is climate controlled. It has sofas, chairs, tables, food, drinks, private bathrooms, private bag checks all before the race. After the race, there will be a hot meal, massages, character greetings, computer results, live feeds of the race, and much more.
For me, it just gives me a great place to relax, eat, and get ready for the race. I like to get there really early to beat the crowds and give my food plenty of time to digest. I have also run the races without using the race retreat tent, but I do feel like the tent made the whole experience much more enjoyable....and magical!!
Let me know if you have any trouble finding it on the website or if you have any other questions!