The ABC Islands, 3 different worlds
They get sold together and sailed together, and people arrive at the second one expecting a slightly different version of the first.
They are not. We did all three off one ship and had three completely different days.
Aruba: the north has no roads
Rent a UTV. Not as a treat, as the only way to get there.
The north of the island has no roads. If you want to see that half of Aruba, you need something built for no road at all, and a rental car will not do it. Everyone who stays on the paved side goes home having seen a resort strip and thinking that was the island.

We took the UTV around the entire island in a day. The natural bridge, the ruins, the lighthouse.

Aruba is dry. There is cactus. It is not the green Caribbean island people picture, and the coastline on the wild side is rugged in a way that is genuinely worth the drive.

We also went through a McDonald's drive-through in the UTV, which I mention because it is the thing my kids still talk about.
Bonaire: kayak the mangroves, skip the snorkeling
The kayaking was lovely. Quiet, shallow, completely different from a beach day, and worth doing.

Then we got in and snorkeled them, and I would not do that part again.
You cannot see much down there, and the roots themselves sting. They are covered in stinging hydroids, which look like little feathery plants and are not plants at all, so you brush past something that looks like seaweed and it gets you. All of us got stung.
Not dangerous and not a ruined day. But the kayak was the good part. The snorkel is an hour I would spend somewhere else.
Curacao: you can rent a car off the ship
No booking, no notice, no arranging it weeks out. You walk off, you rent a car, you go.
That is not true at every port and it changes what the day can be, because you are not tied to an excursion's route or its clock. We drove out to Kokomo Beach and Playa Porto Mari.

Kokomo has swings set out in the water. It is the photo everyone takes there, and it is as good as it looks.

Playa Porto Mari is the one people call Pig Beach, because there are pigs on it. That is the entire pitch and it does not need a better one.
What I would tell you
Plan a different kind of day at each one. The rough north in Aruba, the mangroves in Bonaire, beaches you drive yourself to in Curacao.
Do three beach days instead and you will come home feeling like you saw one island three times. That is the complaint I hear most about these sailings.
And leave one day loose. The best port days are the ones you were not locked into.