"DS is 8 so I guess we'll all share the chores - I'll tell him he has to take his turn or we're not getting a cat"
So he will agree then not stick to it. So you need to be prepared to look after the cat.
If you're going to rescue, think about a black cat. They are the least popular, because of superstition. But it's like owning a mini panther. Black cats wander further and tend to be the least problem.
The multi coloured ones (tortoiseshell) aren't called naughty torti for nothing, but they are very cuddly. They tend to be prolific hunters, though.
As for indoor cats. I doubt that your Son and any friends would remember to not have doors/windows open, for the next ten years. So think how that would work.
You may never be able to open windows again, unless the cat is in. I have been woken up on beautiful summer mornings by a half dead rat brought in via my window. My cat's attitude has been "what's your problem, I've brought you breakfast".
I generally have two cats. One brought in a rat. I thought I'd just shut them in a room and go out until the rat was dead (i couldn't catch it). I came back to find all three chilling together. I eventually shooed the rat out, who thought he was staying.
If they rat they have to be fleed and wormed more regularly. A flea comb is worth getting to check. There's just been a flea epidemic and it's expensive.
Hanging baskets/tubs, mine love to sit in them and eat my roses. I had one cat that ate all the tulips.
Mine scratch at the windows to go out and cone in, anytime within 24 hours.
Cats don't fight to the death, but it's very noisy until they sort out their differences.
Watch "the secret life of cats". Cats are fantastic animals. But they're not always easy.