I would hope the usher's use common sense. If a family is sitting together, with no one else within six feet, and they aren't receiving a complaint, they need to let it go. I plan to go to the game, I will bring my mask and use when needed (ie going to the bathroom, consessions, etc). Otherwise I will sip a drink throughout the game. If there are people outside of my four tix, that are uncomfortable with that, I will work it out/Go sit somewhere else since it sounds like there will be plenty of options). The usher's don't need to police unless they are getting complaints about it.