Well – aged 3 is pushing it a bit I reckon – but thats not just band hero – any of those instrument games would be a bit tricky for really tiny tots I reckon.
Other than that it would be a great present for the kids. Only real advantage is that it has an improved drum controller over the world tour one (I have already had to send my world tour drums back because of a fault).
TBH though the track listing on this game is pretty bad – lots of teeny bopper crap. Might be fine for the kids… but if you fancy playing it yourself then you might want to just buy world tour… lot cheaper… better songs… and you could always buy guitar hero 5 later on if you wanted to expand the song list/ get the new features?