Sharing plates is generally allowed without extra charge at any a la carte restaurant (have seen some posts about a plate charge for Rainforest Cafe.)
Sharing is not permitted at any restaurant requiring per person payment. This includes buffets, family style all you can eat, fixed price restaurants (Akershus or CRT), and dinner shows. It is also not permitted to share the all you can eat skillet at Whispering Canyon without both parties paying for it.
If your child is under 3 years old the child may share at all locations. At buffets you can even provide the child with their own plate.