Yes, we have an ADR at Plaza on 10/31 and my parents will be on the DDP and using a credit that evening. You just need to have the party ticket to stay after 7 p.m. If your ADR was 6:30 and you did not have a MNSSHP ticket, I think you would still get the reservation but have to leave right after. If you made it for 7:30 but didn't have ticket you aint gettin in for your ADR.
I noticed last year during MNSSHP that only a couple of CS places were open. Cosmic Ray's in Tomorrowland and (I think) Pecos Bill in Frontierland. This could be happening later in the evening. I didn't notice until after 9 pm. Guessing Main St. Bakery stays open, but may run out of sandwiches and just have treats. There are plenty of snacks there to use your credits on, but I would rather spend snack credits on F&W plates at Epcot. That saves a ton of money.
