It's hard to say whether a different tube would help without knowing exactly how your son's tubes are getting punctured.

Is he getting pinhole-type punctures along the contact patch of the tire, as if he ran something sharp over? If so, there are some extra-thick "thorn resistant" tubes out there that add some extra puncture resistance, but only because something like a thorn or tack would have to be long enough to reach through the extra thickness of the rubber. They're not really any tougher; just thicker. There are also tubes pre-filled with sealant like "Slime" that can help self-seal some punctures, but again, if that's not the type of flat you're seeing, these tubes won't do you any good.

Or is he getting "snake bite" punctures? These show up on the side of the tube as a pair of holes and are the result of "pinch flats" due to underinflation. If a tire isn't inflated sufficiently to support the weight of the rider, the sidewall of the tire and tube can get pinched between the rim and the road, especially when doing things like jumping curbs or hitting the edge of a pothole. The solution in this case isn't a different tube, but rather to put more pressure in the tire to keep from pinching the tire/tube sidewall.