Having been a Marathon Weekend veteran for hte past 6 years now, I can tell you to find $$ in your budget to stay at the Epcot resorts. Specifically, you want Boardwalk, Yacht and Beach Club, or Swan and Dolphin. You will need to take the bus in the morning to get to the start (and possibly after the half) but for the full you can walk back to the resort. great for a cool down and to keep your legs going. Also, if you have fans coming to cheer yo uon, they can just walk out the back of their resort, watch you go by, then go back ot their room to eat, get ready for hte day, whatever. Only twice have we stayed elsewhere (All Stars and Saratoga) and have been miserable. We've done BC and BW, and my sister came to watch from Dolphin this year, and it was fantastic. Plus, generally speaking, the location is fantastic, close to two parks, lots of dining options close by, best pool at WDW at the B&YC.
As for price, you could run with Team in Training (but you have to raise $$ for them; depends if you're okay with that) or contact a travel agent ot see if they have group rates. I still say book with a travel agent. They will (usually) adjust your price if a special deal comes out and makes your stay cheaper. Don't do the packages offered by Disney. I don't know that they are worth it.
Just MHO. YMMV.
Have a great training year! See you next January!