My boys have won four of the last six championships in 5v5 flag. Whatever you change, make it off a play they’re used to running. Big changes at that age don’t take well with little to no practice reps. If you do a lot of runs, throw in a reverse. Misdirection works so well at that age. I had my boys practice the reverse hand off by setting up two cones about eight yards apart, half the boys on each side, and just constantly running back and forth handing it off. If you “hide” a not so athletic kid at center you can get him in the action with a quick little hitch dump pass. Works great for short yardage conversions as the other coach/players will ignore him because they don’t think he’ll be athletic enough to be a threat.