My fiance wants an open bar at the wedding, but I don't want alcohol at all. What should we do?

Here's why I don't want any alcohol.

My sister is a recovering alcoholic. She's 8.5 years sober. By our wedding, it'll be almost 10 years. Her wedding had no alcohol in it because of this (she got married in 2016). I'm not a drinker myself, and neither is anyone on my side. However, my fiance's family are big drinkers. They drink at every holiday all afternoon, and they even drink at almost every dinner. His dad has at least 3 beers a night with dinner.

I don't want anyone drunk there. I want just champagne for the toast (my immediate family will get sparkling white grape juice because of my sister), but I also don't want the temptation around. My sister is going to be my Maid of Honor like I was in her wedding, and I don't want it to be an issue.

He doesn't think that's fair, but I really just don't want alcohol there. I asked if we could make it a cash bar at least to deter people from getting as much alcohol, but he is adamant on having an open bar because that's what his family wants.

I don't really think he's being reasonable. At least if it's a cash bar, my sister would have to buy alcohol, and I know her husband would not let her. But I don't want her to be singled out by telling the bartender to not serve her specifically. Plus I don't know how well his side of the family handles alcohol outside of his brothers and father. Does anyone have a compromise or suggestion?
My fiance wants an open bar at the wedding, but I don't want alcohol at all. What should we do?
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