Your insurance company might have something to say, too. Policies normally limit the number of people who can be carried.
I once attended a lecture given by Captain Al Haynes, who was the skipper aboard the DC10 that crashed at Sioux City. He said that one of the flight attendants who survived then spent a lifetime campaigning to have the concession whereby infants can be carried on laps removed, after she witnessed an infant dying in horrific circumstances. I've carried my younger 2 children in light aircraft as infants in proper car seats. When children get a bit older, their car 'booster' seats can also be used, effectively strapped in.
My final word about strapping to the lap of an adult... PLEASE DON'T DO IT!
TOO