Unless they raised prices, it used to be $4 for 4 fish in a white paper cup. They go real fast, and the dolphins know who has the goodies.
Yes, have one person stand in line for the food, and another stake a spot on the wall. When you have food, others will squeeze in to pet the dolphins as you feed.
What happens, is that the dolphin notices you have food. They come up, smile, make some noise, you pet them under their nostrum, then toss the fish in their mouth. If you don't toss the fish at this time, they'll splash you and swim away.
You can try to wait for others to leave, but they have trainers walking thru the crowd that will ask you to feed the dolphins before the fish get warm.
There is a snack stand next to the stingray tank. Grab a beer, some snacks, and watch what people are doing.
If you want to feed the stingrays, do it early in the morning as they get full.
For the dolphins, 3pm is a good time to visit, because a trainer comes out with a bucket of fish and feeds certain dolphins, but it happens very fast and you have to be looking for him.
Bring lots of cash and buy at least 4 cups of food.