Well right across from Shamu is the Happy Harbour, so if there's a bit of time, you can ride some rides and let your little one burn off some energy. You'll get reserved seating for the shamu show afterwards, I'm fairly sure.
The Wild Artic is right there as well, with the polar bears, beluga whales, and walrus.
If you head right after entering the park, I'd suggest seeing the Pet's Ahoy show, very cute.
What time is your lunch at? Cause you probably can only see one or two shows before you need to be there. Then once that's over, you can explore the left side of the park, seeing the Sea Lion show, Dolphin Show, pet the stingrays, and see the sharks.