Market Garden is a large grocery store right in the heart of Simpson Bay, at the corner of Billy Folly Rd and Welfare Rd. They have a large selection of of US products and a pretty complete selection of beer, wine and alcohol. For the few dollars you might save to run somewhere else for alcohol, just do it all at Market Garden. It’s fine to bring your own drinks but some places provide chairs and umbrellas, at no cost, if you are ordering from them.