。
Are you having guests for dinner?
Literal
Dinner [to-に] [honorific-お]-guests [object-を] invite-[ongoing-ています]-[question-か]?
お客 is 'guest, customer' with the honorific お- prefix — used universally because guests are always to be honored. 招いている is the resulting-state form of 招く ('to invite'), meaning 'is in the state of having invited' → 'is hosting.' A polite neighborly question.