I got mine an alesis nitro mesh drum kit (has a proper bass drum pedal). Can be found for less than £200 second hand. The mesh heads are more like an acoustic kit (apparently) so any switching between should be ok.
People say the sounds aren't great but I bumped the mids and added a bit of reverb and it actually sounds really good.
Of course children don't always listen to reason so if he likes the g4m kit get him that, can always be sold and replaced if necessary.