When I was trying to do the portfolio for my son I took a half hour and looked over some old pictures and the same for old papers of his. This both jogged my memory for some examples of what he was doing when (esp. when I had jotted dates on things) and some I used in the portfolio (a very complicated wooden train layout he made when he was 3, a bridge he built, some math he did).
And then I told him, I want you to talk about the Revolutionary War for a couple minutes (which was his current passion) and taped it. I was afraid he might not say much, but he surprised me. He was squirmy and all things age nine, but launched into a description of the Battle of Germantown (including that a general was drunk - gotta love that fact). I prompted him with a question or two and that was what I sent. No re-takes or editing. I felt like it really captured him and it was super easy to do. It might be harder with a younger kid, but if you ask them about something they love, you never know what will pop out of their mouths.
