Joseph,
What is the layout like for the field? For example, how many circles could be set up, how big could the pit area be, is there a place for people to set up canopies and how far is parking? I suppose I could do a mapquest and see if I can make sense of it, but your impression about what could be done is probably best.
With respect to a date, don't forget that you have Brodak's the week before Father's day (12-16 Jun 12) and Sig on 23-24 Jun 12. I think that Brad Lapointe also runs something that date as well in Dresden, so the Canadian draw might be reduced. Frank Carlisle ran a contest a few years back at RCCD on the first weekend of June that seemed to not interfere with anything. Perhaps that would be a decent date to consider for this one.
John