I think it's great to start your kids outdoor fun as young as possible. I had both of mine on top of their first munro before they started school. And they walked the whole way. I often had to carry them down though. This was before child carriers!
They are now young adults and still like the outdoors.
Be careful with your storytelling though, or it might come back and bite you!
I took my son on his first wildcamp when he was around 4 or 5. During the day he loved being involved, and gathering wood for a campfire, water for the pot, etc.
Whilst gathering wood, he came back with a triangular piece of white quartz shaped like a tooth. He asked me what it was, and i told him it was a bears tooth. "Cool!" he said.
Later that night, we were sleeping and the wind really picked up and started slamming the tent. "What's that?" said my son. "It's just the wind", said i. "Maybe it's a bear!", said my son. "There are no bears in Scotland", says i. " But you said this was a bears tooth!", says my increasingly nervous son. "I was only joking" says i. "You're just saying that!" says he.
The wind kept slamming the tent and my son was getting more and more upset. In the end, i had to break camp and we went home at 2am to get away from the hungry bears!
Remember there are no bears in Scotland!!!! :)