I actually had an FA light a real candle and stick it in the dessert for the birthday of my seatmate on a flight two years ago. This was not on DL though it was surprisingly a US airline. FA didn't seem too concerned about it, though I wouldn't expect many to act the same way.
There is a 0% chance of the pilot taking the child on a walk-around with a US airline at a US airport. Not even so much because they would be concerned about a 7 year old not being SIDA badged, but more so because of the liability factor of it. If you're lucky though, maybe your flight will depart from a remote stand, in which case you can have a tarmac tour for everyone!
