We did this itinerary last May and had an absolute blast. It was myself, my husband, our 14 year old daughter, and our 11 year old son. These three islands are now our favorites out of all the ones we've been too and we plan to book the exact same cruise for next year.
In Aruba we rented a car from Jay's Car Rental and visited the donkey sanctuary, the ostrich farm, and Baby Beach before dropping the car off and doing some shopping.
In Bonaire we rented golf carts from Bonaire Cruisers and did the South Loop of the island with a stop at the donkey sanctuary. After dropping off the golf carts we had lunch in town and did some shopping.
In Curacao we rented a car through someone in a Curacao visitor's group that I found and spent the morning at Grote Knip Beach followed by walking over the floating bridge, putting our lock on the love locks and then doing some shopping in town.
If you have any questions let me know. We absolutely loved the ABC islands.