If you purchase an under powered plane that you constantly have to fight just to keep in the air that also quickly runs out it's battery charge I can guarantee you won't be around long. If you buy a glow plane trainer and don't seek proper training I can virtually guarantee a similar fate there too as you will most likely quickly crash it.
As stated before, your best bet is with a local club with an instructor. SOME clubs have training planes and a program where you can fly their planes for a few flights to see if you like it. I can not tell you if there is such a club in your area. Check with your local hobby shop.

6 years olds, I don't know. Seems to me that their attention span would be too short to do well. That being said, they are all individuals too. Don't push it on him by any means if it is not his idea. Does he really have the eye/hand coordination that this will require? Difficult for you to judge since you have not been trained yet yourself. Some young kids can be amazing though.

To be double-double-redundant, go check out what the hobby is really all about at a local club field and find some of your answers there too, We'll keep trying to help though.
We would like to see you in the hobby but I'm not going to tell you that learning is instant or easy(with a few exceptions). It is fun though. It is a matter of learning a new skill set