Back on topic. Start them as young or old as you want, let them try both. Expose them to other kids that are skiing/riding. Kids learn by seeing, doing and playing. Playing and enjoying the snow is the key...in HI saw like 2 year olds surfing...on the board with mom/dad or standing up, dad pushing the board and kid falling and swimming. Just let them have fun and learn joys of playing in the snow.