Just bare in mind that you'll only get this reaction from that type of person in this country. But I'd say just try to avoid photographing kids in the UK at the moment - even if you do feel strongly about it, it's not really worth campaigning for.
I've got a feeling some people here will be repulsed by this idea, but... this can't be emphasised enough for street photographers - dress up a little bit. A summery smart/casual pale coloured shirt, slim fit black jeans and chukka/desert boots is a good 'blend-in' look at the moment. Street photography is a social activity. Treat it like a street party at which you're the official photographer. Your appearance and confidence because of it is everything in this situation and exudes a casual authority about what you're doing. A hoody two sizes too big, baggy jeans and walking trainers, of course - you'll be lucky to get to the shops for a pack of ciggies without someone shouting tramp, never mind take people's picture.
I'm sure nobody ever screams pedo at Scott Schuman for example (the Sartorialist).
Clothes are an important part of photography often not given enough thought - whether you're photographing windswept landscapes or weddings, it certainly matters.