Welcome to the forum!! You are going to LOVE Aruba, and while this will be your first trip, it will not be your last. You mentioned that you both like outdoor and hiking type activities? You may want to try walking to the top of Mt.Hoiiberg, and you may want to try one of the ATV Tours of the island. Culture wise you will be arriving after Carnival, so you will be missing out on that, however you can check out the Bon Bini Festival at Fort Zoutman on Tuesday evenings in the capital city of Oranjestad. And there is the Carruban Festival in San Nicholas on Thursday nights, lots of fun.
Thank you for yet more great suggestions! I'm writing them down. I am a photographer and plan to come home with some amazing photos, so some of these tours and cruises sound wonderful! (I did get my photo added to my profile. Maybe it'll show up in this reply?)
Welcome to the forum! Aruba has some great opportunities to capture with a camera. Sunrises and sunset can be spectacular as well as the beaches along the southwest facing coast and the more rugged north and east coasts. We leave in 20 days and I'm still sorting out what gear to bring this time!