Judy Moody and Friends-Not-So-Lucky Lefty by Megan McDonald illustrated by Erwin Madrid*

My eight year old loves this series and any book with Stink Moody in it.
Stink and his father are left-handed.  They celebrate Left Handers Day together.  This year Judy wants to join in their festivities.  They acquiesce IF she will only use her left hand all day!
The day holds a lot of laughter (Stink and dad) and frustration (Judy).
*Highly recommend.
-Borrowed from the library.