First and foremost, read Gina's trip reports - extremely detailed account of everything.
Your gut is telling you correctly, but a few weeks out, the website will post a schedule of showtimes. It is possible to do all of the shows, but make a plan. The online map does not do justice the length of the walk over and back to Shamu Stadium, not something you want to do more often than needed. So, plan which Shamu show and make the trek once...see Wild Arctic while you are over there. Also, don't forget there are some great aquariums with some of the rides, you don't need to ride the rides to see them.
We loved the reserved seating, but we got it free with staying at a partner hotel. It is not necessary, but it is nice. We did purchase it for the Christmas shows, but that is a little different situation than yours.
You do not have to ride the Penguin ride to see the penguins, but I will still recommend it. They have a mild side with very little movement, and the "reveal" is worth it! Also, keep in mind, it is COLD!!!!
Same thing for Wild Arctic, you do not have to ride the ride to see the Belugas and walrus.
I guess my best advice (especially taking out rides) is to look at the schedule and make a plan. The shows are so good!!! If you are a foodie, consider the all day dining plan. If not - look at Gina's new thread with pictures of the menus and see which shows are nearby the food you would like to eat. Lastly, don't rush and enjoy all of the scenery and animals.