The kids take it in turn doing a variety of things, so that we don't have arguments every single night over who gets to choose teethbrushing things, who gets to be first to get put into pyjamas, who gets to check inside the parcel box when we get home, who gets to choose who gets out of the bath first, etc. This month, Sophia has odd numbered days and Gideon has even numbered days. Except that they swapped yesterday and today so that Gideon could have his birthday.
Except...that a few months ago we used the app
Chwazi, where everyone puts their finger on the screen and then it picks someone (to be first player in a game, for instance). And Gideon loved it. So last weekend when I asked who should get out of the bath first he said "We'll play the finger game." - and I asked him if he'd be sad if he didn't win, and he said no, and then he and Sophia played it, and he lost, and I had to wash the hair of a sobbing child, who kept saying "I thought I would win!"
So this weekend, I asked him who was getting out of the bath first, and he said "Finger game!" and I said "Do you remember how sad you were?" and he said "Very sad!" and I said "So you should just choose." and he said "I have a plan, this time the person who loses will go first." And, of course, he won. And so, again, I had to wash the hair of a crying child who thought he'd found a way to beat probability.
All of which is to say that if you want to beat people at games of chance then I recommend 5-year-olds, who are both terrible at understanding it, and completely fail to learn from that.