the younger kid made the mistake of not reraising. Would have been a great play though if he held something like KK or AA and induced you to reraise with a weaker hand. But that wasn't the case

Dont beat yourself up about this one AJ is not the hand you want to be reraising into a pot with someone all in. The other player with 77, is getting pretty good odds on any reraise you make. Figure there is now $210 in the pot if you play this hand, how much do you have left to reraise??? Unless you have $200 more in front of you you most likely dont have enough to make him fold. If you reraise all in for less than $100 more he is going to call you for pot odds. The play he made is also something I would do to draw another player into my pot with a big pair, something that has you dominated. It is always frustrating to sit at a table with someone like this pretty much giving away his money and not be able to get any of it, but this situation the best thing you can be hoping for is a coin flip. There is a decent chance that you could also get yourself into a pot where you are calling with a dominated hand.

Yeah, I see what you're saying. My point was that judging by his reaction and the way he went about calling the all in, I figured him for a low-mid pair and thought he would fold if I came back over the top, which he said he probably would have. I wasn't operating under the notion that I was ahead of the caller, but rather under the notion that if I reraised he would fold.