Yes, they can. They are basically ordering off Kona Cafe's kids menu.
Children can either do the buffet for the child's buffet price ($10 or $11, not sure), or they can order from the child's menu for less (about $5 or $6). You should not be charged the buffet price for a separate child's meal. A good server will "work with you" on this if your child is uncertain about the buffet.