It doesn't matter which day you show up.
They key to enjoying your day at SWF is to arrive early and do the 2 roller coasters in the back of the park. They let people in at 08:45am, so arrive the parking lot at 08:30am. National Anthem plays at 09:00am, and you start walking, head to the left side and go straight back past dolphin stadium. Take your rides on JTA and Kracken, it will be a walkon and you can go many times.
Watch the dolphin show, the first one usually starts at 10:00am, then head over the Clyde and Seamore. For each of these shows, get there 20 minutes in advance for good seats, 30 minutes if you want the front middle section. It doesn't matter, you can see everything no matter where you sit.
For the polar bear exhibit, do the walk thru, the simulator will make you sick.
Eat lunch at 11am or 3pm. At noon everyone gets hungry like you wouldn't believe and the lines for the food places are nuts. Even if you are not hungry at 11am, go to the food place of your choice, order, and eat.
3pm is a good time to visit the keywest area, buy a beer at the snack stand next to the sting ray tank, and feed the dolphins. They play Jimmy Buffett music and it feels like Key West. By this time, your feet will be tired, and you'll be ready to leave.