I usually use a bobber of some sort with young kids, you can still bobber a senko or a fluke and reel and twitch it, the fish in ponds around here aren't offended at all by that presentation and it keeps me from having to unsnag or retie the kids lure every 5 minutes. My favorite version of this is one of those little crappie jigs under a Styrofoam bobber, they catch fish and have fun and I can fish in between taking bream off their lines. You probably have plenty of stuff that would work fine, if he is just learning to cast, in the spirit of safety and not wanting him to have a bad experience I would avoid treble hooks for the time being, if you've fished with young kids enough you know one of them or you has gotten hooked on wild casts before, a hook in the back will ruin a fishing day real fast for a kid. Floating worms and senkos sink so slowly that as long as he is so-so reeling hes likely to never touch bottom, a light wire hook will do most of the work by itself as far a hooksets go.