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.
A lesson on the importance of encouraging your children with their projects - https://news.ycombinator.com/item?id=2757980 - July 2011 (103 comments)
Never say 'no' to something unless there's an obvious safety issue.
Especially don't say 'no' just because you don't understand the request: that's the time to show them that you're curious about what they're thinking and give them practice explaining their reasoning in a safe and comfortable situation. Kids need freedom to explore their world.