Just my 2 cents, I live in the country and have a nice big mowed field and from the time my grandkids could toddle around i would put them on my lap and ride around on garden tractors, then would teach them how to operate as they got older, some were 6 and 7 when they would drive by themselves(with grampa walking beside with an eagle eye on them) then i would introduce them to the mini bike riding behind me, then eventually on their own.(always made them ware helmets). I taught them how to check the oil and fill the gas and some repairs. Heck one was riding minibike at 5 better than a 10 year old(Kids are not all alike in development, maturity, ect.) anyways i think its important to take the time and try to impart your knowledge as soon as you can on the next generation. as far as riding on my motorcycle with me, i agree they need to be big enough to touch the pegs.