Havn't been to Cheeky Monkeys in a while, but I understand it's been done up and is much nicer than it used to be.
I'd go to Cannon Hall Farm though. A little futher out (a few miles S of Hudds on way to Barnsley), but brilliant day out, farm, palyground, park, cafe, fresh air, farm shop - what more could you want. DS (2) could spend all day in the playground.
Leapfrogs OK, v close to me, but a but big and rough and never my first choice of soft play. Cakes always stale too.
OF course, the Zone! My DS is 2 though and too big for baby bit but too small for big bit by himself, which means I spend a lot of time going round big bit with him, and steep, scary slides. Nice juice though.