Would be fun kid hideout space! Awesome dog kennel under the stairs design idea. If you want an indoor dog house, utilizing the space under the stairs for a cozy, attractive and practical space for dogs is a good idea! I love this design.
Great idea for entertainment & favors.some sort of circus/carnival game with this as the "prize" board. Let kids choose a prize for answering questions about the birthday boy/girl or a trivia question.