If Eunice and Steve believe the husband's friendship is valuable for their art business purposes, then they need to figure out a way to maintain the relationship so that the husband still likes them. But that doesn't mean inviting them to their home. I would return the double dipper's call and apologize for the delayed reply, state they've been SO BUSY, but would love to get together and just plan to have drinks with her and her husband someplace. Basically, socialize with them a bit, but don't invite them to your house where she can ruin the food, and if she says something else offensive you can make excuses and exit the place ASAP politely instead of ignoring it and seething in your own home.
Better yet, drop by the gallery and chat with the husband. Talk business, maybe grab lunch. Maintain that relationship but don't socialize with the wife. Bean dip her and don't be pressured to include her in future invites. Be polite and friendly, but beandip on the parties. If they are close to any mutual friends who are invited, talk to the mutual friends and ask them to please not blab about the party, because times are tough and you had to reduce the invite list and you don't want anyone to have any hurt feelings if they were not invited this year.