One of my favorite memories with my older children was making nature journals. My niece has been staying with me, and I decided to let the kids make nature journals.
The journal's I did with my older kids were more detailed, of course, but for a five, and two year old, I just decided to let them gather items, and tape them to a page. I then put the page in a page protector, and into a folder.
They think it's super fun, and are always looking for anything they can bring home and put in their nature journals.
As they get older, I will have them do extra things in their journals. They can draw a picture of the tree that they got a leaf from. They can write a paragraph about a tree, flower, anything they put in their book. They can take photographs.
You can add anything, really, to a nature journal. My oldest son's has snake skins! UGH!!
But this is an easy way to start toddlers, and young children, who don't have much of an attention span, on nature journals.