ugh.....
I am the father of 6 year old twins....Both have fished with me a number of times, and each is better than the last...
I, too, had NOTHING but trouble with those cheap Snoopy closed faced jobs, and ended up throwing them all away. I simply bought two identical VERY SMALL spinning rigs, and spooled with cheapo line. (The whole 9 yards cost less then $40 for both) We then spent a couple of hours having a "casting tournament" in our backyard at a hula hoop, with a plastic practive plug. They picked it up pretty quickly, and pretty much perceived the whole thing as a game.
I DO NOT let them do the casting while in the boat as of yet.....But hey, with small bobbers, worms, smiles, sunnies, etc., who wouldn't want to be right there anyway???
When we camped on shore, I let them wade in a foot or two, and let them cast their brains out...That was safe, and worked beautifully. They did catch fish - WHICH IS THE KEY!!!-It makes them want to keep going.
Little do they know that pop's evil plan is to co-op their little minds, so that I have a built-in permanent excuse to go fishin'!!
Best of luck, and certainly best of times!!
Zuke.