Wow, good question and lots of thoughtful response. My parents accidentally let me tour another So cal park, called Knott's Berry Farm, on my own when I was seven. Our group split up around dinner time, one to get food, the other to get the sweatshirts our of the locker. Each group thought I went with the other. I just calmly went to the prescribed meeting place and waited. I don't recall my parents being overly concerned, especially since they didn't know I was missing until after the fact and since that was the kind of kid I was, but I definitely don't think it was intentional!
As a lot of folks said, I think knowing your kid and their street smarts and awareness of their surroundings is important. Your question is a good one and I hope you arrive at a decision that works for your family.