What game are Zach, Alice, and Poppy playing in Chapter One of the novel, Doll Bones?

Zach, Alice and Poppy indulge in a regular game of make-believe in which they have created an entire kingdom that is set in times of pirates and even more fantastic creations like mermaids. The characters in the game are portrayed by various dolls and action figures and the “set” is areas near Poppy’s house.