6yo finds the film too scary -> 12y texts mum who comes to collect 6yo
6yo drops drink all down himself -> 12y texts mum who comes to collect
6yo or tells 12y he will be ok to stay wet
6yo gets picked on by someone being a prat ->12y texts mum who tells cinema staff to sort out the "prat" or 12y alerts staff to the "prat"
6yo falls over and smacks his head open in the dark -> a rather rare occurence I would think, however 12y texts mum who comes to collect 6yo
6yo argues with 12yo re doing anything and refuses to do as told -> mum tells them both in advance of expectations, who is in charge and to what extent - and that if 6y doesn't do as told he will have to leave; if 6y does argue, etc then 12y texts mum who comes to collect 6yo
12yo finds power goes to his head and bosses 6yo about and 6yo rebels and runs off and hides -> mum tells them both in advance of expectations, who is in charge and to what extent - and any arguments/issues with bossiness or not listening then they will both have to leave and it won't ever happen again; however - if an issue and 6y hides then 12y texts mum who comes to collect 6yo (and 12y if being bossy)
6yo wonders off and the 12yo doesn't notice as they're watching the film -> again, another rare occurrence I would think; 12y told to put 6y on inside of her, not next to aisle; if 6y did go missing then 12y to alert mum immediately and also to alert cinema staff
6yo wants to go to the toiler and 12yo doesnt want to take him -> 12y told of expectations beforehand and 6y told he only goes if necessary; most children ime can manage 90 minutes without a week. However 12y must take if need be; see above re never happening again if any issues.