regardless so long as your boyfriend isn't bothered there's nothing wrong with simply saying "thank you - but no" just be flattered. from my observation anyways unless you really push it too far yourself that's all it takes for a guy to get the message and leave you be.
Just watch the drinking and keep it at that. Nothing wrong with a little flirty fun -- but it can be easy to lose sight of boundaries in the heat of the moment, particularly when you're brain's numb and your spirit's lubricated.