My children are extremely helpful in the garden. The question is what is the best age to starting delegating gardening responsibilities. Young children should know that vegetables don't just come from the grocery store. My son is only two so he his knowledge of seasonal gardening is limited. I plan on teaching him a lot this year. Beans are the perfect plant to start with, because they are big enough to fit in their little hands comfortably.
Simply soaking a seed will jump start the seed into sprouting in a day or two. This will give the child the option to remember that the seed has changed from its original state. I would suggest using beans such as hyacinth, fava beans, or even a scarlet runner.
I once used a method of starting a bean in a a jar so my kids can watch them grow. It was a perfect way for the child to watch the bean swell, loose its protective shell, develop roots and sprout leaves.
The method of growing beans in a jar is better for a child between the age of 4 and 7. At that age kids have a better understanding. Please watch the video below to watch my son talk about growing hyacinth beans inside of a jar.