Manny’s Cows: the Niagara Falls tale by Suzy Becker.
Manny is a farmboy who cannot go on vacation like the rest of the kids in his class because he has to take care of the 500 cows on the farm.  I mean, what is he supposed to do, take them with him?  Well, that is exactly what he does by loading them all into buses and heading off to Niagara Falls.  At first, the cows are less than enthusiastic about the trip, but they get into the spirit.  And eventually when Manny finds himself broke and far from home, the cows save the day.  The book is filled with clever puns, great asides, and lots of laughter.  It is made even funnier by the illustrations that often feel more like a comic book than a picture book. 
This is not a book to read to a group, but one to share with children in elementary school who like a good giggle and enjoy pure silliness.  The illustrations are too detailed for them to project well enough to a crowd, and one would not want to skip any of the wry comments made by the cows on their travels.