S.G.
I went to a wedding where someone walked around with a video camera and everyone got the chance to share a special memory they had of the couple.
You could designate someone to do that at the retirement party or even hire someone to do it.
By the way, it is so nice to read a postitive post about a MIL on here for once. It seems like everyone is always complaining about theirs and I always think "am I the only one who likes my MIL."