So most of the gym is usable for all ages except for the weights and training area (14+), top rope and lead rope require classes+certification test, but the auto belay (the rope climbing wall with a device that allows you to rappel on your own) is usable by everyone also. Passes are for the entire day unless specified otherwise, and the gym gym is mostly open until midnight and most holidays.
They don't bill by time, a pass is all day as others mentioned.
Your pass is good for the whole day
You can stay all day. 4 is a good age to start.
We took our son there when he was 4 and he loved it. I think you pay by how long you are there, bit I'm not sure.
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