Sorry if this replicates another thread! I couldn't see one, though.
Wallingford Bunkfest is over the weekend of 3rd-5th Sept. It's a really family-friendly event, with open-air and marquee music (folk and roots), vintage steam trains, lots of children's activities, etc. Oh, and a rather good beer festival. 
I meant to meet up with other local MNers the last couple of years but didn't manage to. If anyone's taking their DC (we will be taking DS during the day, and then looking for a baby-sitter so we can do the saturday evening concert) and fancies meeting up...?