For stingray city we booked on our own through Capt Marvin. Disney's Stingray City excursion didn't allow under 3 of age. However we were so happy with Capt Marvin that we would use them again instead of Disney. Don't recall $$, but they have a website with all that (Google them).
Did Dolphins through Disney to keep it simple. Trip was fine. Their prices will be listed on their stuff.