I'd like to see her side of the story, why she was in the bag in the first place (but why was it left out?) and how she spilled the drink. Now, I'm not suggesting she's an innocent little lamb and it sounds like the behavior was wild, but with nothing for a kid to do and inattentive parents .... kids are going to act out.

It sucks to have these issues at your wedding, but to me the bag thing sounds a bit petty. Did the spill ruin your pictures or anything? I personally think, to steal a line I've seen another redditor use, you need to make like Elsa and let it go at least for now and at least in relation to other people's events. You can set your own boundaries for how and when you interact with this family unit, but agonizing about how to deal with this all at other people's future family events seems a bit drama-seeking.

Kids ran around at my wedding. There were spills and my dress got stepped on and someone put a finger in my cake icing before we cut it. I adore my nieces and nephews and was not perturbed by any of this, and was happy my brothers and sisters were having fun talking to friends and relatives.