While optional, your luau booking includes free admission to Sea Life Park on the same day or within a year after the luau. The popular events (included in your luau ticket price) include the dolphin show, penguin trainer talk, and sea lion show.
Please note that the park closes at 4 pm, so if doing same day, you would need to hang out until check-in opens around 5 pm. There is an area in the park with an open cafe, shaded seating, bathrooms, etc. where you can wait until the luau check-in begins.
The luau transportation service arrives around 5 pm so it does not sync with visiting the Park during the day. However, if you wanted to visit the Park during the day without a car, you could take Uber/Lyft there and just take the transport service back to Waikiki/Honolulu after the luau. Please proceed with booking the transport service when choosing your package and simply note that you only need return service; the price is the same.