I encourage parents that I meet to do something like what the author of this post has done. These days, photos are ubiquitous. Curated memories in your voice are a rarified treasure.
My father encouraged me to journal, but I only really started when my kids were born. For many years now I have kept a private blog that tells the stories of their childhood. They're still young but have already read through it many times. Now, when we are on an adventure, they often remind me to jot something down in my notes to be added to the next entry.