Never had issue with children at gigs, God knows its hard enough to get them away from computer games and into live events at the best of times. Mine have been going to gigs for years, although when in their mid teens I was relagated to dropping off and picking up - on the plus side it meant I didn't have to see Lost Prophets or My Chem Romance, but felt it my duty to go and watch Stone Sour / Slipknott, obviously.
On the other hand i used to be dragged along to 60s festivals at Butlins (dreadful bands, brilliant people & drinking) and swathes of pushchairs used to clog up the 3 concert halls. If that ever happened at 'proper gigs' then it would need to be looked at. Never happen though with our sensible Health & Safety laws, oh hang on...
Have more issue with screaming babies (and couldn't care less parents) in Costa when Im trying to enjoy my massively price inflated coffee & caramel slice to be honest.