What if Marty doesn't like my party?

"Marty is the coolest kid in Henry's class. When Henry invites her to his birthday party-and she says yes!-he spirals into a web of worry and anxiety. His head spins with all the potential reasons why Marty might not have fun at his party. What if Marty doesn't like his dog? What if she doesn't like Grandma's special birthday cake? What if the elevator in their apartment building is broken and Marty has to walk up the stairs? As Henry and his sis...