Nobody ever taught me to disconnect BOTH lines when draining the tank. Maybe that's wrong, but seems to me the air will get sucked in through the muffler, along with any residuals which will just gunk up your muffler.

And as far as electrics and human danger: I've read too many stories about accidentally bumping the throttle and turning the Tx on with the throttle not at zero, or reversed and causing bodily harm. At least with glow, you have to put in a little effort to start that saw.

Now having said all that, it's so cool that you have your son at the field with you. I'd give anything to have my 5-year old boy get the bug from his dad and want to fly RC. He loves airplanes, but at this point it's all combat flight simulator on the PC. I read so many posts from sons who's dads turned them onto this hobby. Very cool.