Scout offence reps

You didn't say how old the kids are. For older kids (say 12+), you can draw up the plays and show them in the huddle. If you're going to do that, it helps if you can color code it - X is red, Y is Green, Z is blue, TB is Orange, etc. and just tell the kids to look for their color on each play diagram ("Okay, Billy, you're playing Z, so just look for the blue "O" and do what the blue line indicates.")

With younger kids, even with a color-coded diagram, it's going to take forever to get the play explained and then they'll still run it wrong most of the time. You're probably better off just setting up a line and having the coaches run all the back & receiver positions (assuming you have enough coaches to do so).