Stick them in the left hand seat get them start the engine.
let them fly it.
Just treat them as any other 10-13 year old.
I wouldn't do loops, most kids that age are more than happy with some gentle bunts and a steep turn or two. Its the letting them fly the thing that will be a buzz.
Do the take off and then start pattering left hand down a bit, gentle pressure back etc and then once you up then get explain what the controls do including a good boot of rudder. Then see what they want to do, if they want some bunts do one or two and then let them do one or two. If they don't and just want to fly around with you saying left a bit right abit etc then do that.