Ian,
I voted for July, but any would really work. I just figured July would be warmer and less chance of rain. As for location, I do like the sound of the facilites at Walled Lake, but I'm wondering about how we go about getting our boats on with no public launch.
Booze isn't a major factor, but it is nice to enjoy an adult beverage or two in the sun

What about Elizabeth Lake the Club Royale is on? Especially if they are going to help sponsor things.