Although I'm no kid, I used to visit the flight deck in flight whenever I flew a non-U.S. carrier. Even prior to 9/11, U.S. carriers did not allow in-flight flight deck visits. I have even sat in the jumpseat for landing into both ORD and LHR on Virgin Atlantic A340s, a reall treat. These days, your only option is to visit before or after the flight. There will eb no exceptions made for kids in-flight, whcih is a shame, but probably a reasonable restriction. Judging from the number of flight deck photos on Airliners.net, people are still getting into the flight deck when the plane is on the ground (and maybe even in flight, although I suspect many of the photographers for the in-flight photos are pilots).