If they are also having their honeymoon at Disney, I would get them a Disney gift card-we were so grateful for those gifts at our own Disney wedding and we were able to buy lots of fun things on our honeymoon that we wouldn't have, had we not received the gift cards
I would say that if you do buy them a thing instead of a gift card, have it shipped to their home so they don't have to pack it to get it home.
Otherwise, if you want to have a gift basket sent to their room at the resort, that might be fun (if it's stuff they can use/eat on their trip). Check out Disney Floral & Gifts: http://www.disneyflorist.com/
If they are honeymooning in Disney I'd get them a gift card they can use just make sure its not for just the stores and can be used anywhere disney. If they are honeymooning elsewhere it may be nice to have a beautiful basket arrive the day they come home to welcome them back.