I've got 6 kids ages 14 to 2 years. My pinball machines are all out in the shop, so the younger ones don't have much unsupervised time with the machines. Besides, there are a lot more dangerous things out there besides the pinball machines. My older kids are pretty responsible, and I don't mind them going out there and playing unsupervised. When we have friends over, I will open up the large sliding door on the side of the shop, and since the shop makes up one side of our small back yard, it is pretty easy for me to keep an eye on things.