We have a fantastic page that suggest
Things to do in Aruba. You could spend a day at the
beach and partake in water sports, go on a cruise, play golf, visit a
casino, visit the
Lourdes Grotto and much much more.
You mention the people staying are in their 20s so i would suggest you look at the information we have on the
Aruba Nightlife and hopefully this will give you even more ideas on what to do on your trip.