I worried about this happening when I used a child seat on various bikes when the Groms were Small Things. I read of the risk, and deliberately avoided putting the seats on some frames. Well so much for my smart arse comments. Now...the dent. They can play on the mind, but these ones, in this location, are in my view fine. Aesthetic pain I know. but they are fine. I have some steel bikes which I acquired with considerable dents. They are fine. And a Cannondale which had a HUGE kink in one chainstay - I rode it for years just to see what would happen. Nothing. Nothing at all. I'd attribute your dents to 'patina' and just remember your kids being tiny when you look at the frame in 15 years' time.
I dropped a hard heavy thing from a shelf the other day, onto my blue BfEMax. It simply scratched it, but I was ridiculously upset. I got the paint out, touched up and got over it. Although clearly I can still remember it or I wouldn't be writing this...grrrrrr