Its simple just ask them what they would like.
I have had blind trial flights. You just talk them through it just like when you let a blind person have a shot of a car (not on the public road I might add) I even let a blind person drive a 45 ton lorry and reverse it into a garage.
In my experence blind 10 and 13 years olds are little buggers just like sighted kids and enjoy the same stuff.
One thing you can do though thats slightly different is to let them run there hands over everything including the engine. Don't worry about sharp bits just tell them they are coming up to a sharp bit and put there hands gently on it.
As for on the controls not a problem just do a running commentry and don't be tempted to cover the controls because they will know.
With the older ones I have done Effects of controls and they loved it.