We actually didn't see any of the shows at all, and we ended up going for a day and a half (with a break at midday). So I would vote for missing the shows - we had a great time feeding sea lions, rays (eeeew!), and the dolphins at the end of the day - MOBBED at first feeding. We enjoyed the polar tour, the manatees (because they're my FAVORITE). I suppose the penguin area wasn't super great, because we were going on the tour and were going to pet a penguin. There's also the clydesdales you might want to skip, and there's a large section of small kids rides in the rear right side of the park that you could skip.
When you go in, head straight toward dolphins and see what time the feeding is. If there's not TOO much of a line, you should do them first since they're hungriest then. Later in the day go back to the rays (which you'll run by to get to the dolphins), since they'll always eat. The sea lions are way up so try to fit them in, but I'm pretty sure feeding the dolphins is def. the busiest.
Have fun!