What if you billed “daddy” for providing day care? 
obviously not in your eyes, especially since in acting that way you could also blow off a certain amount of your work, and complain incessently on line about how poorly behaved other people were, I see it was a win-win-win for you.
OTOH - consider your position for the future - Sir tagalong had no negative consequences for bringing his ill mannered child to work, is unaware others had problems with it, and has no particular reason to not do so again. Only the next time, you’ll have the additional problem of explaining: “well if it bothered you so much last time, why didn’t you say something?”
That was my point wrt to the “not stranger” thing - this is someone who you will be working w/ 8 hours per day 5 days a week for the foreseeable future. It’s unreasonable to expect that this situation will never happen again especially since you’ve allowed him to think it wasn’t a problem.
But no fear, you can again open up this thread or a new one and bitch about how poorly other people are behaving and how they’re not being responsible, complaining about all that work you can’t get done due to the distraction etc (not to mention having to post all of the updates ohmygod it sounds like he broke something!).
Only don’t be surprised if not everyone agrees that you’re selection of ‘what to do’ is the best.