I understand that you wouldn't tell other people's children.
Do you have children of your own? Because I am thinking that you are young. Disneyworld wasn't opened until the 70s, so I am thinking you are younger than me.
I just don't know of any parents that tell their kids that the characters at Disneyland (or Chuck E Cheese) are not real. What about seeing a magic act? I don't know of any parents telling their kids that the magician is just using tricks and doesn't really use "magic".
No I don't have children yet. My children would know that fairy tales and myths are stories that are fictional accounts.
My parents didn't have to tell me that the characters at Disney World or Chuck E. Cheese weren't real. But no, I didn't see magic acts, considering what the Bible says about magic.
From infancy, I was taught the truth from God's Word the Bible. By the time I was old enough to even remember going to those places, I knew the difference between fictional characters and real people. It honestly didn't lessen my enjoyment at all. I did believe that music on the radio was being played by live bands actually in the studios. I found out the truth about that on my own, but if I had asked my parents, they would have chuckled and told me the basics. They would NOT have said, "Yes dear, that's right, live bands!".
My parents read us Bible stories at night. They told us funny stories from their own childhood. By the time I knew how to read, I LOVED reading fantasy stories and fairy tales, but I knew they weren't REAL. I think I would have enjoyed them LESS if I had thought that they were real. Fantasy worlds strike me as being very arbitrary and there is no loving God in them.
My older brother is very outgoing and affable, loves people. When he went to kindergarten, at Christmastime, he took it upon himself to tell everyone the truth about Christmas. The school asked my parents to keep him at home, and they agreed, that was appropriate for the situation. However, we were encouraged to tell the truth and share the Bible with people whenever possible. For example, we talked about evolution vs. creation with our teachers. I don't think there is anything evil or sinister about the truth. I think it is beautiful, and eminently more satisfying than any myth.