I am not familiar with the rods that you chose so I can not tell you whether they would be favorable to teaching flycasting but remember that 13 and 14 y.o's are rather old and very physically capable in the whole scheme of things.
I have a taught younger kids how to cast and I have found that not necssarily a slower rod is better but I have noticed that 7 and 8 weights are easier for newbies to cast because they can 'feel' that line in the air and 'feel' what is going on with that line a little easier.
Hope that helps...
Ryan S. Petzold
aka Sparkey and/or Special