I think Labor Day weekend is the best date.
As much as I like dispersed camping, I think you should utilize a campground this year so we can have a campfire.
Maybe have easier and more difficult trail options. I'd love to test out my 410 lb bike shod in knobbies on some moderate trails, and maybe borrow Kimberly's DR350 for the extreme stuff? She doesn't have a lot of riding experience, so she'd probably do the big bike ride on the 350.