"First, I only have 4 mags for my M&P 9. Looks like I'll be shooting in Production division, do you think will this be enough? Hopefully I won't miss much."
Shouldn't really be a problem. I just carry 5 (and sometimes 6) because I'm paranoid, and have managed in the past to fling a perfectly good full magazine downrange when I was trying to reload. So I bring extra. If you don't do anything nearly that stupid, you'll be fine.
(Or in case I have a faulty mag for some reason--though I shoot Glock, so mags are not nearly the problem that they can be in other guns.) And like Chris said, someone else will probably be shooting an M&P there, and so if you need one, someone will probably let you borrow a mag.
"Second, I'm debating what holster to use. I have an el cheapo nylon think thats works ok, but I also have a home made Kydex holster that seems to work really well. It retains the gun well and draws fast, but I'm concerned that I may not have covered the trigger guard well enough."
I agree with Chris, that you should just bring both and have people take a look. It would be better if the whole trigger guard was covered, but technically as long as the trigger isn't accessible (and it looks like it isn't) you'll be fine.
The one thing extra I _would_ say is that don't worry about really fast draws.
Unless the stage is a 3-second burner (and I don't think any of them will be) taking an extra 0.5 second on the draw won't make any difference at all, comparatively, and you are much more likely to have a safe, perfect grip on the gun otherwise---which will make your shooting faster and better.
See you there!
