Uhh, there are really not much electronic drum kits under 1000 bucks, try a real drum kit, make sure your son can keep a beat, let him suffer til' he gets his beats down, then just get him a real drum kit. he'd probably be happier and have more fun, im 14, i did this as well, i suffered for months, 4 to be exact, and i used some virtual drum kits online, and i used my friends drum kits, and i learn to be good, or at least half descent before i got my own drum kit, so test him a little, and get him some drums, not some plastic pads, after he gets some skill down

Thats all i did, and now me and my dad play together and we sound amazing. this is before christmas, and im posting after, so this might not come in handy.