Boxed wine?

Our guests will only see the sangria that is displayed in really pretty dispensers. Other than that, they won't see the wine being poured. It's in an old boyscout camp, so they have a service window instead of a bar. My parents have a Costco membership so I can ask to go with them one day to check out prices. I'm planning on doing a red wine sangria and a white wine sangria using moscato. I'll have one red wine option and one white for guests who choose not to drink the sangria. Along with some kegs that have yet to be determined. We also have cocktail hour, but that will be various alcohol in cans and bottles since there won't be a bartender.

I agree that there are some decent boxed wines (like black box and bota) and they store well and hold a lot, which is nice.
But definitely please avoid the suuppppeer cheap stuff like franzia... bad quality leads to BAD hangovers

There are some really good boxed wines (BotaBox and Black Box are my favorites). I might suggest getting bottles for the white wines though. Most wedding bar setups do not have refrigeration and keeping a white, boxed wine chilled requires taking the bladder out of the box to put on ice and then it's a pain in the butt to pour.