my daughters are 14 and 9. they have been around my ball pythons since the days they were born.(the kids, not the snakes....) they began handling them at around the ages of 2 or so. so i would say that 4 and 6 is plenty old enough for a ball. of course, there should only be supervised handling and proper education. i'm a believer that the sooner they can be introduced and learn about them the more confidence they will have around the snakes and the more respect they will have for them as part of the family.