So this is what an hour on the internet and a phone call will get ya.
Gunnison has an airport that appears accessable from any major airport in the US. There are 3 other airports within 3 hours drive, Denver,Aspen and Colorado Springs.
I found this place for lodging.
http://www.3riversresort.com/other.htm
60-100 people, no problem. They do big groups often. It looks like it would run $30-65 a night depending upon what you want as far as rooms etc.. It all depends on how comfortable you are with sharing space. They have single rooms up to houses for 8, and everything in between.
There is no place for camping or RV's but there is a State campground about 2 miles away and a private campground about 4 miles away.
They do have meeting areas available both inside and out (reserved for a fee).
The property is located right between Gunnison and Crested Butte. About 10 miles from each as far as I can tell.
Best time of year for us would probably be August 15- September 15.
The only downside I see really is the lack of camping/RV spaces. Whith the price of fuel and the somewhat reasonable price of lodging, that may not be an issue.
This is no more than an example guy's.