It's a great FREE few hours with lots of attractions for the children plus green space and a not bad play park.
It really is a free event and if you bring a picnic it can be quite easy to have an active few hours at no cost.
Usually there's quite a few different sports, a climbing wall, some animals, bouncy stuff of sorts, bikes for all abilities and some arts/ crafts type stuff.
VPX more info here
Mine were ranging 5 - 12 last year. Eldest starting to lose interest, but it's a bit noisy for him, middle at 10 and youngest at 5 both loved it.