These were my favorite Devotional books with my children:
TODDLER THROUGH PRESCHOOL:
The One Year Devotions for Preschoolers (Little Blessings Line) by Chrystal Bowman
There is a second book, The One Year Devotions for Preschoolers by Carla Barnhill that also looks very good, but I haven't personally read this one.
PRESCHOOL THROUGH ELEMENTARY:
My Big Book of 5-minute Devotions by Pamela and Douglas Kennedy
As a side note, this book is a compilation of Five Minute Devotions for Children and More Five Minute Devotions for Children.