I can fully recommend a man called John Rayment 'Crazy Balloon Modelling'. Look him up at email@example.com.
He was brilliant with the children at my sons recent 4th birthday party at Deen City Farm. He did modelling, face painting and tattoos. He also did some games so we didn't have to do any entertaining at all which was great as it rained the whole time.
Lots of parents at the party really liked him too.