Well, how about waiting until Sept. 16th for more sign ups. At that point, you can decide how many teams to create and do the first drawing for teams. Let's say if another 8 guys sign up by then, I'd do a random draw for 10 3 man teams. Then maybe say that Nov. 1st is the dead line to get on a team. SO after 10 more guys sign up, then do a random draw of them and place them on the original 10 teams. SO hypothetically speaking, if a total of 100 guys/gals sign up by Nov. 1st, you'd end up with 10 10 man teams. Make Nov. 1st deadline for sign up.
But the contest could start by Oct. 1st with 10 teams of maybe 3 guys/gals, or more if 10 more people sign up. Just keep the numbers even on each team throughout the sign up period.
As far as ending the contest. I'd say about the end of Feb. or end of March. Most guys are done calling by then.
Just more ideas!