This sounds like a lot of fun! If I may, I'd like to suggest that you come up with some prices for gals who go to these things solo ... not with friends/family. I know there's a lot of us out there who would go to something like this but don't because the prices for one person can get kind of high.
Also, how about having a fun event where everyone (who wants to) can participate right there at the Retreat. I put together a bus trip one time and found the folks loved something simple but didn't require much effort on their parts. Besides, we sure did entertain the bus driver! I've got a couple of suggestions if you're interested. Just PM me.
I'm in Michigan so please be sure to post the dates here when you get it all together.