Ok, just adding a few of my thoughts:

- There is also the idea of a recipe wedding book I really like. You'll have to contact all guests beforehand (Your daughter probably has all their email adresses. That's cheaper and faster than snail mail) and tell them to bring an A4 paper (and tell them the page orientation - portrait or landscape) with their well wishes and a family recipe for the newly weds to try.

- I always liked this tutorial. It's for a baby shower but it could just as well be adapted for a wedding quilt, using your daughter's favourite colours.

- If you decide to go the classical guestbook route, you might want to check into individual papers that can later be bound to a book. That way, several people at once can work on it, you can leave the paper plus some pens at the table and check back later or have them bring it to a specified table. That way, you'll get more out of the whole reception as well, as you don't have to wait on people to finish writing their well wishes.