[Arubalisa]

http://www.jolly-pirates.com/ Jolly Pirates goes to the wreck of the Antilla. Because you are not going to be on the island very long I would take the shorter afternoon snorkel which would give you the morning to enjoy the beach.

I would do the same as well with an island tour. In 4 hours you can see the highlights of the island.
Aruba's Finest Land Tour with Kini Kini http://www.kinikini.com/kk/servlet/Tours is sufficient for a first time visitor without having to spend eight hours riding around. Again, this gives you half a day at your resort to enjoy it's amenities.

Instead of a sunset cruise, could I suggest a sunset dinner on the beach for your anniversary?
http://www.aruba.com/forum/tags/sunset%20dinner.html

Enjoy!