Honestly, I'd put everyone in Ouray, CO. There's camping, small town feel, and the most amazing scenery in the state. The Million Dollar Highway is right there and it just doesn't get much better. We can route down to Telluride, Lake City, Silverton, and elsewhere, we can nekkid hottub in the Orvis Hot Springs, we can even ride an old style train down to Durango if ya like (heck, send the wives down on the train 'n meet 'em in Durango and loop on back up. Haul ass down there on the twisties on stuff that'd scare 'em silly and go easy back).
It's fairly high altitude with several mountain crossings so I'd go june to early Sept, with my fave time of year (Mountain Flowers) being late July to first week in August. It's about six hours from where I live.
All this being said...there's a LOT of really stunning places to stay in CO for an event like this; I've been to Valkyrie rallies here before as well as many other types (I'm also into fourwheelin'). How many folks generally attend? What's the level of organization? (I'm new to the Rocket world)