Cuddle up with a friend or two and read a children's book!
You can find out more information about Children's Book Week here. There's descriptions of activities and stores participating in CBW. You can also get a free bookmark by Grace Lin or order the fantastic poster, by Hugo Cabret creator Brian Selznick:
Isn't it great? It brings to mind one of Selznick's self-professed childhood favorites: Fortunately by Remy Charlip.