Even for regular service, I allow my musicians to enjoy a glass of wine or two. Having worked a ton of weddings, it’s all about your own professionalism. If the wedding couple or host in general says it’s ok, then I have no argument. They are paying for it! As an owner/planner I monitor and make sure my team knows to watch the serve. They shouldn’t, and I haven’t ever seen, photographers or the band take advantage or slam back shots. This is why you choose your team carefully :)