Hi Melissa, Congratulations on your upcoming wedding!
You are right, Disney will be the perfect way to celebrate your new family. I think a wonderful "bonding" idea for your daughter and husband-to-be is the
Dolphins in Depth Tour. Several years ago, we arranged for our oldest daughter to do this with my brother (her uncle). They had a blast together. It was one of those "once-in-a-lifetime" experiences, and she will always remember who she shared it with. I answered a previous guest question about the Dolphins in Depth Tour, and you may find that information helpful. You can read it:
HERE.
Another idea would be for them to rent
Sea Raycers (minimum age of 12 to rent). They would have so much fun zipping around in the waterways together.
Hope this helps and that you have a wonderful wedding, Magical honeymoon and live happily-ever-after together :)
Kaylene