The answer is no for all casinos. The required age for getting inside a casino is strictly 18 or 21, depending on the state. Casinos risk being fined huge amounts of money if they are caught granting entry to minors. It will probably be alright for minors to walk around other parts of the casino but never in the gaming area. Even if the idea is just to let the minor watch, the rule remains.
Another issue is whether you can sneak in a minor to play with you in the casino. This is possible in some casinos, especially if they look older than their age. The problem is that even if they can play, they won’t be able to claim their money if they win. Also, casino personnel occasionally ask for IDs when they suspect someone of being under-aged. If you don’t want to risk getting kicked out of the casino, this isn’t a good idea.
Another issue is whether you can sneak in a minor to play with you in the casino. This is possible in some casinos, especially if they look older than their age. The problem is that even if they can play, they won’t be able to claim their money if they win. Also, casino personnel occasionally ask for IDs when they suspect someone of being under-aged. If you don’t want to risk getting kicked out of the casino, this isn’t a good idea.