How to tell guests no shots?

So let me first say we have an open bar. We don't have a problem with people casually drinking for our cocktail hour/reception and we are happy to provide that for them. However, FH and I are concerned about shots. Part of my family is very conservative and will be unhappy there's free alcohol served anyways (they're old school and my aunt is a recovering alcoholic so it's a touchy subject). I find shots at a wedding tacky (personal opinion). We want to create a classy wedding atmosphere and people doing shots just doesn't fit our vision. So my question is how do we relate this info to guests? I was going to just let the bartender tell them, but I'm worried people will be pushy towards her. Thoughts?