There are plenty of ways to help kids plant an edible garden, make a fairy house, build a fort, etc. And they are more than capable of figuring out things for themselves as well. But I remember how happy kits made me when I was a kid...
A good kit enables you to focus on the goal of putting something together or creating something. It's almost like getting a gift; you feel a spark upon opening a container full of new things to assemble.
I found a nice assortment of outdoor kits fit for Spring:
(Images: as linked above)