Charlie the Ranch Dog by Ree Drummond (The Pioneer Woman)
I usually teach the song first, then read the book, singing the song on each page turn. Then we learn the instrument parts and add the instruments. My students love Charlie. You can also go to the Pioneer Woman's blog and show the students the real Charlie and the other ranch animals.
We also use this same song and instrumentation for the other Charlie books - Charlie and the Christmas Kitty (change the second line from "he works hard all day" to "he loves Christmas Day" and Charlie Goes to School (change the second line to "goes to school each day".