What about York Maize? I'ts £8 of an adult and £7 for children but there are family tickets you can also get. We took our tribe there a few weeks ago and had a fab time, loads for them to do apart from the maze when you get in. Tractor rides, small farm, pig racing, big jumping pillow, inflatable maze. We spent all day there and it was great. Just wear old shoes as it can be muddy in places!