I own both of the dresses below & have worn them quite successfully for large meals. The trick is in the high, almost empire waist, & lots of fullness from the ribs down.
This is a good year-round dress, hidden in the Clearance at Boden, sized generously. I wore it on Thanksgiving with navy tights, an aubergine scarf, & boots.
This dress can be dressed up or down. I got it in Petite, so it'd be a bit shorter. It's a good year-round ponte knit material that doesn't cling, & most of us women who own it like the pockets (see reviews). The waist is higher than it looks--closer to empire--allowing for plenty of expansion below the waist.
I wore this one for high tea with some friends & looked & felt just fine after stuffing myself with finger sandwiches, scones with jam & clotted cream, & petit fours :-) (fond memories :-)
What do you wear when you know you'll be eating a lot? Enjoy those holiday meals! :-)