Hi do kids have to pay under 11 years of age

I am not sure Kids under 11 would quite get understanding of the Trap Museum in context !!!

When I was there I didn't see any children in line at all..

It depends when is at the door. I haven't had to pay the last 2 times I went.

Yes, I believe there is a fee for everyone. I did not witness any children present during our visit. I recommend calling ahead to check in advance.