I did this for my son's wedding reception. I made a heart wreath wall hanging on which I embroidered MY wishes for their marriage. I thought about micron pens, but those can be very frustrating for the uninitiated, so I provided fine point sharpies in 5 or 6 colors. One person at my table offered to take it to the next table....and so on. Nearly everyone signed. One of the first people to sign drew around her toddler's hand, then signed and wrote well wishes inside that. Subsequently, several others did as well. Perhaps because there were several pens and they don't look like everyone's normal pens, I did not have any pens disappear. My daughter in law and her mother, as well as several wedding guests told me how much they liked the idea.
My original idea was just to give the couple my wall hanging. The signature idea was an afterthought from my DH, but a huge improvement.