I always book my child as an adult. I've done this ever since he had to sit on my lap (with extended belts) on a UK internal flight with the worlds favourite airline. OK he was only three at the time.
What is the difference to aircrews on this issue?
Also, often it's cheaper for me to buy him a grown up ticket than it is to buy him a childs ticket. The only thing I can think of is a weight / balance question, but I'm a tad chunky so we balance out.
I've been asked once to move him at a check in gate and allow a fare paying passenger to have the seat but once I showed the ticket they accepted his right to his paid for seat - but they said that I booked under false pretenses and they would consider removing me from the plane. Fortunately they didn't.
So whats the beef people?
PS. I think cabin crew do a great job and I'm not a nasty customer.