If we have dining reservations for 5 people, and only 4 people show up, what happens? We have reservations for O'hana's dinner, LTT lunch, and Chefs de France lunch.
Nothing. You should be fine. If it is a credit card backed reservation, they will only charge you if no one in your party shows up for the reservation.
Nothing. We planned a trip once to take our niece, had all our ADRs set, but then she couldn't go
We called to change our ADRs but the cm told us we'd likely completely lose our res as we were too close & that 3 ppl get the sane table as 4 so no issues. Make sure you tell at checkin that you are 4 bc you won't need a table for 6 to be seated