a collage of the pair of you growing up.
For both DS and DD's graduations from HS, parents were given a small poster size piece of paper to fill with pictures of the graduate.
I cut and overlapped filling the entire paper with images from baby to current. I made sure I put a picture of DH with child somewhere and child/me.
DS or DS with past pets, everything. Makes for a colorful eye candy effect when one collages.
Call around to find where it can be laminated, We have a copy place in a strip mall nearby.
If you like the idea, I will try to post one of the collages I made so you can use it as a model.