There are a number of mum and baby groups but not sure which ones run through the school holidays if any. When my daughter was that age I attended the lovely nct mums and babes group held on a Friday morning at St faiths church near north dulwich station (dont need to be a nct member), I know that doesn't run in the holidays. I believe there is also a Nct mums and babes on a Monday morning at goose green church hall but I never went to that one. I also liked going to the group on a Monday afternoon at the Albrighton centre (on the estate opposite sainsburys on dog kennel hill) for babies under 18 months, we didn't start going until my daughter was 5months but you will be fine going with a younger baby, again not running in the holidays. Also check out this website http://www.edtots.co.uk/ lists things going on in east dulwich.