Dude, that would be a complete dick move unless your baby never
cries (which isn't possible)
Just think about when you go to the movies & any number of other people are there, whispering behind you, straight up carrying on conversations during the movie and/or effing around with their cell phones in front of you the entire time doing God knows what. My guess is that it bothers the piss out of you whether it's opening day or 4 weeks after initial release.
You want to bring your 3 week old baby to the biggest movie of the year on opening day and you're a member of this site? Wow
I can't believe people think that would be cool. I'd honestly be the first person to come straight up to you and tell you to leave if your baby cried once and if you refused I'd get management involved.