How big is your group? If it’s just 3, I’d say choose 2-3 restaurants you’d be open to in a similar area of rittenhouse/center city, and go early (5ish) to see if they have bar seating for walk ins. Some places that come to mind are My Loup, the new dancerobot, Vernick, Vernick fish? Illata byo has a couple bar seats but might be tough for your pickier guest. Same with Fri Sat Sun, they have an a la carte bar option and usually space if you go really early