October should be good. We may get the odd freak storm then but generally that hfs of until the end of October-beginning of November. That time of year is around when we go moose hunting early season and the muskeg isn't frozen. I can actually only remember one year where we had snow in early moose season. Lately it's been unseasonably warm.
I would bring decoys. Buying them here would likely be more expensive and I don't know anywhere that rents them. If your friends are into hunting you may want to buy a bunch for them and leave them up there. Save you hauling them the next time.
SS
ETA: Canadian thanksgiving is October 12th.
Last edited by SamSteele; 08/01/15.