Taking the Crinkleroot Guide concept one step further and also borrowing an idea from Flat Stanley, the famous paper traveler, how about having a paper Crinkleroot accompany your family on this month's nature adventures.
We printed an image from the internet (I wanted it bigger but it lost clarity as I enlarged). You could also enlarge a copy from one of the books. Cut it out (we put a construction paper backing on it to make it sturdier and added a popsicle stick handle) and he's ready to go along on nature walks and assist with the studies. Here's where he went with us today.
Here's one printable image of Crinkleroot: http://jimarnosky.com/factpage.html
Joann's contribution: Crinkleroot w/ an added idea for older children