Some popular ideas include:
A personalized mug: Buy a kit at the craft store and have the children paint or color the mug for their father.
Picture frame: Either buy an inexpensive frame for the children to decorate or they can make their own gluing together Popsicle sticks or craft sticks. Place a photo of the child(ren) in the frame as a keepsake.
A book written for fathers: The book can be a children's book about a father's love for his children that your Dad Boss can read to his children or a book written for father's in family section of a book store.
A personalized t-shirt, cap, or tie: Using fabric paints children can personalize clothing for their father.
Hand print stepping stone: Kits for hand print stepping stones are available at craft stores.
Tennis balls or golf balls: What sport does the father play? Purchase equipment for the sport.
Sports team t-shirts or caps: Find the father's favorite sports team clothing at a local sports store.
What are you doing for your Dad Boss for Father's Day?