Pray. Just kidding. Before you start anything, rules, behavior/classroom management, expectations, mechanics of the class (where to go and what to do when you get there). Stations are always good (depending on how much equipment you have). Set up multiple games of the same game. Reach out to a local college for students who are pursuing their KIN degree and want to be teachers. At CSUEB, we had classes that required this for credit. Parents volunteers. Good luck.

I agree with CFoott. Try and get student teachers every semester. I've had 35-40 students but with two teachers. Split the class into two groups and monitor from the middle of gym. You could have both groups perform the same activity.

I have taught elementary PE for the past 24 years in Texas. The class size you mention is very manageable. I average roughly 65 kids per class k-5 at a time for 45 minutes. My students come to my class four times a week. Every Friday I have every single child which means I have 88 kids at one time. We do large group activities such as yoga, dance, walk, jogging, and running laps on Friday's. I also have access to a program called Adventure to Fitness which we use on Friday. Cooperative games are a great way to start out the school year. I do parachute activities 2-3 a year for an entire week using both large and small ones. I had 110 kids at one time my very first year and it taught me a lot. Hang in there.