|Children should be able to see adults drinking responsibly and not using alcohol as a medication
I think that medication can be one of the most responsible ways to use alcohol. I'm aware that there are people who use "medicinal purposes" as their excuse for pathological binge drinking, and THAT isn't good for children to see, but genuine medicinal use of alcohol is fine, IMO.
For example, my mom has a bone problem that causes episodes of severe pain. Anti-inflammatory drugs don't help, and she hates the way narcotic prescription drugs make her feel clumsy and stupid and sleepy. When she's in pain, she would rather sip a double shot of hard liquor while cooking dinner, which dulls the pain enough that she can cook and eat and talk with her family, than take addictive opiates and lie in bed being useless. She isn't addicted to alcohol and rarely drinks for any other reason. I grew up seeing this behavior, and I don't think it inspired any irresponsible behavior. Actually, for my brother, the idea that alcohol is a medicine made him puzzled as to why anyone would use it recreationally!
I now have a health problem (severe headaches) that not only can't be treated by alcohol but can be triggered by alcohol, so I mostly stopped drinking 5 years ago. My son sees me take communion (real wine at our church) and we've been to a seder where he had a shot glass of grape juice to drink at the times when the adults had wine. My partner drinks at parties sometimes.
We just brought EnviroBaby to two adult parties this past weekend, so I was thinking about this issue. Of course we discourage him from grabbing people's cups, no matter what they contain, because we don't want him to spill or drool in them. He's used to the idea that he can't always drink what his parents are drinking because we don't let him have hot drinks. If these were the kind of party where people are really stumblingly drunk, or if it were crowded, I'd be concerned about him getting stepped on. However, nobody at these parties was intoxicated beyond the point of being a little giggly and dramatic. He was enjoying watching the silliness, but I think he knew something was up: Of the people who are fond of him and like to pick him up and such, he avoided those who were tipsy--he'd interact from across the room, but he didn't go over near them--until they started acting normal again. Very smart of him to avoid people whose coordination is impaired.
I don't mind exposing him to these situations if he uses them to refine his self-protecting skills.