D.P.
Use a camcorder to record everyone's wise marriage advice and compile it into a DVD for them to keep.
I love the matting of the photo--what a great keepsake that will be.
Also, you could compile photos from their childhood and put a show together with meaningful background music. His love: pics of her growing up, Her love: pix of him as a kid and his kids, Their love: pix of them together.
It can be shown on a continuous loop at the party or maybe before a toast by the hosts?