I have not seen any instructional material specifically for kids for pool (unlike say tennis or baseball where kids leagues are huge), but I've been around junior players and leagues for years.
The start is always boring to the kids who expect to be taught how to shoot jump shots their first day LOL.
For beginners, once you get though how to hold the cue and the stance, it's just shooting a line or a circle of balls directly without the cueball.
Once they can aim that way to get the majority of shots in, you can start with the cueball. Same basic drill, a simple line of balls around the foot spot (for younger players you'd want to go across the short side of the table, say the middle going side to side pocket, cueball a diamond away, shoot with ball in hand down the table.
After about 4-5 repetitions of this, you'd need a break, maybe get them in a huddle and explain things like contact points, why you need to line up the right way (show them what happens when you hit the ball off center by accident or wave the tip around during the shot), go back to the drill for a few more times after going over some corrections with them.
Speed control (or at least teaching the awareness that it's important to hit soft at times, medium at times, and hard at times) can be started early, otherwise the kids will either hit too soft because they are afraid, or the boys will be hitting everything at full speed to show off. Have a lag game with the winner getting a case or a cheap cue or break cue, or chalk holder, etc... Lagging the ball will also help them see what happens when you hit on the side of the ball as I'm sure they will send the balls all over the table hehe.
