House opens 30 minutes before curtain, which is standard. However, the line to go in starts easily getting ready a full hour before curtain. (It doesn't really take that long to get folks in)
BUT....if you got them through TM re-sale, I wouldn't worry....they are fully in control of those tickets. (Stub Hub and the like is a different story, with reason for concern.)
After the show? It will take some time to find out who is coming and and whatnot, so your timing is likely going to be fine. NO, they shouldn't wait inside the theater, they have to clean and prep and get ready for the evening show, and they are not a babysitting service. Yes, your kids will be fine waiting outside the theater for you. Another option, is to find a coffee shop for them to meet you at, they can can a drink and a snack and not worry about weather or whatnot.
If we're not having fun, then why are we doing it?
These are DISCUSSION boards, not mutual admiration boards. Discussion only occurs when we are willing to hear what others are thinking, regardless of whether it is alignment to our own thoughts.