Just thought I'd recommend some parks. Beddington has a lovely playground and loos, Mordern Hall has enough in the way of streams to keep small DCs playing pooh sticks for hours, and my New Favourite for hot days has to be Croydon Road Recreation Ground. It's got a paddling pool. A real, proper, municipal concrete paddling pool. THat is drained every day, clear of broken glass, free from slime and dogshit - and totally wonderful. Take 2 changes of clothes for DCs and a towel (Cos I forgot the towel and spare shoes and had to re-dress rather damp DS).
Anyway, hope this is of use.