Hey there Stowaways...
So many great suggestions already we'd be hard pressed to offer additional - but, while this one may sound quirky, if by chance you're archers - the Colorado Bowhunters Association annual Jamboree is the weekend (4 days) of the 17th this year.
It'll be near the San Isabel NF, close to Twin Lakes. Boondocking only, but there are some RV parks up the road south of Leadville. Lots of 3d ranges, rolling sage, good fishing, always a hoe-down, and very family friendly.
Just thought I'd toss it out there...