Personal preference, but I would go with photography. Since they have photographers on grounds, I would take advantage and set up a photo shoot with them. Since you're in-laws are with you, you could have some really nice photos taken as a couple, then with your in-laws. It might not be something you would spend money on at home, but being it's "free" money, and the location is amazing, what better place to capture those memories?
And if you're anything like me, it's so hard to get a photo of the both of you. Unless it's those silly self-portraits (which we do ALL THE TIME!). To me, having some great images of me and my hubby would be priceless.