That's wonderful! Donkeys roam many islands in the Caribbean, or at least the ones where they haven't been killed off because they were considered "pests" after cars were introduced. I'm glad the people of Aruba chose a different solution.
If I'm not mistaken there is a tour you can take to see the donkeys. I'm sure there is also a fee to take the tour. You can see the donkeys from the vehicle but since they are wild I doubt very much you'd get to pet or ride them, unless they have some tame ones around.