[StevieG]

Since you expect a lot of inexperience players, I would suggest offering "training classes" at lunch for a few days up to the event, maybe even a week. Have a sign-up and teach 8 or 9 (maybe even 10) each session. Possibly, you can even do them as a quick $2 sit-n-go with a nominal prize that earns a little more for your charity.

This will eliminate the need for tutoring in thr tournament (when you are very busy), as well as introduce the concept and maybe hook some who would jump into the tournament for money directly.

None of the buy-ins go to a prize pool, these are recreational players at best, and you are worried about how long it will go after work. Forget add-ons and rebuys, I think. If you want to make sure your charity gets a higher take, increase the buy-in.

You have plenty of increase in the levels you can expect this to wrap in maybe 5 hours or so. The levels are short at 15 minutes.