It's worth it to keep checking B&C and A&C as things are always opening up. You might consider using one of the free reservation finders such as through Touring Plans to look for you (still up to you to log in and book it). Not sure of your party size but I just looked at 6pm for a party of 4 on 10/31 and A&C did have availability at 6:20 and 7:45pm. Ale & Compass Lounge (off YC lobby) and Martha's Vineyard Lounge (in BC) are both first come first serve and offering some food/snacks. I was there last weekend and one night there was a wait and another it was very easy to walk into either. Also worth noting that A&C is available via room service at the Yacht Club. The quick serve market at Yacht Club is pretty good in my view and mobile ordering is available.
Trattoria al Forno (table service) is open across the lake on the Boardwalk. I believe the Boardwalk Pizza Window and Boardwalk Bakery (both QS) are also open so you could grab something there and eat on the Boardwalk or even bring back to your room. Also, in the Swan, Il Mulino (Italian) is open and has reservations available both on the Disney site as well as opentable. Il Mulino is a bit more upscale but have seen kids in there many times (again don't know your party).
If the Dolphin does open, agree the Fountain is terrific as is their quick serve market.
Hope you have a great trip!