As Geemo said, you need to include everyone in the reservation. It's partially for table sizing, but it's also to make sure the restaurant doesn't exceed the fire code capacity. DLR is using the same cancellation policy as WDW; it's $10 per person on the reservation for no shows. Like WDW, it's kind of ambiguous whether "1 Day" means 24-hours, anytime the day before, or something in between. The DLR website used to explicitly say cancellations must be made by 11:59 pm the day before the reservation (so 11:59 pm on Monday for a Tuesday reservation), but that language was removed and it went to the vague "1 Day" wording.