Relax, poohs4me, you got this! If you have not been to Hawaii before, then I would recommend checking the Activities list at the Aulani site (it is down in the fine print near the end of the main Aulani web page).
Once you see Activities, under the heading Pool Areas, you will see Poolside Cabanas. Click on that and you should see a number to call for reservations. (I guess the number was posted while I was typing.) I did not see a way to reserve directly online, though there might be one.
Also, under Activities, if you click "Excursions," you will see a whole list of possible side trips. These include dolphin encounters, kayaking, surfing, zip lines, a walking tour of Waimea Valley, a tour focused on movie locations, Pearl Harbor tours, and a "Wild Boar" off-road expedition. If the spa is open, I cannot recommend highly enough planning to go there. I recommend scheduling that for your last day, if your flight leaves in the evening from Honolulu. I would also recommend checking out the Viator site for trips. The ones that leave from Ko'olina or pick you up at your resort will probably be the most convenient. You don't want a trip from Maui unless you will be on that island. Disney had a shopping shuttle trip to Honolulu when we were there. I liked the Dole plantation tour, though it is admittedly a bit of a tourist trap--but a nice one, and of a variety that you cannot find elsewhere. At the Dole plantation store, they had a "Pick a Pearl" site (really, pick an oyster), and I selected one that had a lovely black pearl. I have acquired white, pink, golden, and silver pearls that way at the Japan pavilion in Epcot, but never a black pearl there.
I think that you will find anything to be enchanting, if the type of activity appeals to you. My favorite excursion was a snorkeling trip, reserved through Ocean Joy--you may need to go through the Viator page to find that. I am not sure if the sea turtles will be around during a snorkeling trip in May (they were not there on a trip we took in March, but were there in August). Whale watching should be great in season--the trip we reserved was canceled due to weather though. I think reserving a whale-watching tour in the morning gives you better odds of avoiding cancellation. The Polynesian sailing canoe trip that we took was also excellent; this tour left right from the lagoon at Aulani.
I also recommend Roy's very highly as a restaurant for dinner, if you want to eat somewhere away from Aulani. It is within walking distance, or you can take a resort shuttle, if they are running.
We are planning to go back, but possibly not until 2023. My idea for the return trip is to alternate days that are 100% at Aulani, enjoying what the resort has to offer, with days that include an excursion.
You will have a wonderful time!