Enjoy hanging out with the kids and teaching them stuff.
If they are little kid beginners make sure you ask them to do things that aren't too hard. Do things like toss the ball to them and have them hit the ball into the fence. (sometimes they will hit it over the fence, so think about what is on the other side of the fence). Have them hit it along the ground to each other. Have one of the kids toss the ball and have the other kid hit it. The pair that hits the most, or hits the most into a target area like in the court over the net or an area on the fence wins. Kids like to compete. Maybe even whomever picks up the most balls and puts them in the basket wins.
Everything so that they have fun, and if they are not same level of ability, so that everyone has portion of fun. Use games with balls, racquets and court rather than teach them strokes. From just getting used to all the stuff progress to games related to basics. Anyway, make them move all class long - it's an activity first of all.
Ah eh and the forehand lag-release fo sure so that they have the correct habits from the day 1!