I take my baby to baby cinema every week and I love it. But it means if she is a bit grizzly, doesn't matter. I can carry her in in her car seat but she sits on my lap, watches film, snoozes etc
I am taking her to a non baby cinema showing of Finding Dory as DH wants to go so we will take her to a weekend morning showing where crucially there are other children but her car seat won't go in. She'll go in the sling and sit on our laps.
I'm sorry I really don't think it's fair to take a baby to an evening screening of a film when other people have gone there for an adult evening. Take your baby to a parent & baby screening or go to one earlier in the day.
As for those asking about ratings. Infants under 1 are exempt from the 15 rating, but only at the individual cinemas discretion. The big chains Cineworld, Odeon etc have a blanket ban on anyone under 15. The Independents tend to be a bit more flexible. So I had to take DD with me to parent & baby for Ab Fab at Everyman as my local cinema Empire wasn't showing it, and I checked with Everyman to make sure it wasn't a mistake.
If you decide to take your baby, don't take the car seat or pushchair, there simply isn't room. And a normal showing doesn't have to accommodate your car seat because it WILL be in the way of other seats/ people
Just sit baby on your lap or in your arms