I think gardening is a fine thing for kids to do. Gardening is a physical AND spiritual activity.
It's also a learing activity.....in my case for both mom and daughter, it's amazing the things I have learned from and about her while we've been digging in the dirt together.
She's been messing around in the veggie patch with me since before she was born. Her birthday is in July and I wanted to make sure I had a good supply of fresh produce after she was born so I was planting while pregnant, and would have her out there with me once I started harvesting. She'll be 10 this July and is still my favorite gardening companion (along with daddy)