We just did this in January on the Horizon - such a wonderful itinerary, and it's great to be there until late.
In Aruba, after our beach day was done, we went back to the ship to shower and change then caught a cab literally right outside the ship. There is a man in charge of taxis who will call one for you. I recommend going to the Palm Beach area - it is PACKED with awesome restaurants and shops, all walkable. We walked around and checked out menus before having dinner at Tango Argentine Grill. Definitely recommend. Then we walked around some more before catching a cab back to the ship.
In Bonaire, we again did a day excursion then back to the ship to shower and change. Right outside the port are some shops and restaurants; not as much or as beautiful as Aruba, but there are options. I suggest heading out of the port and taking the main road to the left - just past the "I love Bonaire" sign - and walk a few minutes to Gio's Gelateria for some awesome (and CHEAP!) gelato; it will be on the right. Then head toward the water and you can have dinner or a drink at Karel's Beach Bar while watching the sunset.
Have a great trip!