I'd recommend keeping your lesson plan on a card or piece of paper to bring with you in your pocket or in your bag. Unless you have a lot of experience teaching kids it's tough to go out here with only a mental plan because things can move faster or slower than you expect. Also, keep the lesson plan flexible, have some options available in case something isn't working out right. What do you do if only 3 kids show up that day? What if 8 or 9 kids show up?
King of the court is a great game, but if the kids aren't able to play out points it gets old really fast. It turns into them missing the feed over and over again or at best a 1 or 2 shot rally. Giving them a second (or even third) chance at a feed is fine, but you can't give them infinite chances because then it holds up the rest of the kids in line and also the king on the other side may start complaining that its not fair. If they can't play out points then a game like jail works well to keep them from being discouraged.
One more suggestion - even if they can't hit the broad side of a barn, set up targets or power ups in the court (when doing drills where there is no one on the other side of the net) to get them to think about hitting to a target rather than just trying to bunt it anywhere inside the lines. We used anything we could find like a hula hoop, a towel, even the cart itself. If they hit a target then they win a piece of candy, they are excused from picking up balls, or they get to keep hitting while the rest of the class has to run a lap.