What ever happened to just enjoying the company of your companions and not your device. I have worked in areas where no electronic devices allowed. It allows for more conversation. If the need for device is more important than enjoying your vacation maybe stay in the buffet.
Two off the wall suggestions. The food hall inside La Cote Ingles has a full wine section. Also Carrefour on Las Ramblas. It’s a big supermarket with a full wine selection at great prices
As a NY native I would not hire a car for the Rockefeller Center tree or Saks ad where it’s located on 5th Avenue is a parking lot during that time. Take public transportation plus the view is better