In Sweden I was surprised at the the gambling games aimed at kids at fairs/theme parks. Roulette/wheel of fortune gambling to win big bags of sweets and chocolates. In the UK I think you'd at least have to introduce an element of skill into the game. (Also I've never seen so much candy for sale as in Sweden! It's amazing Swedes have any teeth left.).
Swedish kids are in general only allowed sweets on Saturdays which helps. That actually leads on to a pretty dark story too long to write in this margin, but Wikipedia has a good summary: https://en.wikipedia.org/wiki/Vipeholm_experiments
