We went last year over marathon weekend b/c DH did the Goofy Challenge. There were travel agents putting together packages for marathon weekend, but they weren't necessarily the best deal. We just went with the AAA price at first, and then they released the VISA codes (room rate discount and free park hopper/water park add on to the tix) and we were able to switch to that, which was a better deal than the AAA discount.
There is a marathon package available.
You could look on-line and see what a room only res will cost and then call and inquire about the package to get an idea of what works best for you.
I called and received a quote. 5 days at CSR 2 adults and 2 kids 6 day PH, right at $2000. I asked if I could add on a DDP and wa told no. They do not offer the DDP with the marathon package.
The biggest advantage is you can book the package now and switch if they offer a better deal later.
If you want the DDP, I would just wait a bit more and book a 2009 package. According to the Dis rumor mill, release is just around the corner in August any way.
I called Disney this morning and they told me they didn't have any packages or special rates for marathoners. I went ahead and booked WL and a ridiculous rate (that we can't afford!), but I'm sure there will be a code or discount once rates are released for 2009. We just really have our heart set on WL, so I wanted to make sure we have a room reserved.
Okay, I just looked online, and the marathon package with tix for our family is only about $100 more than what I booked for room alone on the phone. But, I was unable to get a quote for room only because it said you could only book through 12/08 online.