Thanks for any suggestions!
What about Old Mother West Wind or Children of Noisy Village? Pippi Longstocking? Mr. Popper's Penguins? All of a Kind Family? The Borrowers?
You have such a wide range in ages of children that I am not sure you are going to find something that will captivate all of them, but then again, who knows! As far as I know, there is no such Treasury of Stories so you will just have to seek out good family chapter books.
While browsing online last night I found this amazing free resource of old stories for children! Many of the stories involve faries and children exploring the outdoors! There are hundreds of stories that I think will be perfect! Here is the link: http://www.childrensbooksonline.org/library.htm