Welcome aboard, Penelope! Setting sail on the newly re-imagined Disney Magic is going to be a fabulous experience for your family! I have been able to sail twice on the Magic since it was re-imagined and can tell you from experience that you are in for some really amazing treats!
The Disney Fantasy and Dream offer the Midship Detective Agency interactive game, as you mentioned. Unfortunately, the Disney Magic does not have this same game. However, they have added tons of new and only available on the Magic touches. If you have kids, they won't want to miss
Become Iron Man in the new Oceaneer Club. There they can virtually be fitted in Iron Man's suit and watch their suit come to life as they move in the virtual booth, seeing the suit move right along with them. This is offered a few times throughout the sailing, and sometimes even during Open House hours when parents get to stay in the Club with their kiddos, so keep an eye on your Personal Navigator for this!
If you enjoy exploring the ship and "hunting" things down as you did in the Midship Detective Agency, you might want to pick up a copy of "Hidden Mickeys Go To Sea", a book that walks you through clues to help find where Mickey shapes are hidden throughout the ships. Though I don't think there is an updated version since the Magic was re-imagined, I know that plenty of the original hidden Mickeys are still in the same spots onboard that ship, so you'll be kept busy with the current version of the book! My kids absolutely love hunting hidden Mickeys, and my husband and I enjoy spotting them ourselves as well!
Have fun planning your cruise, Penelope!