When i was a child, in the late 50s and early 60s, kids were not allowed in any pubs. If my sister and parents and I visited one, Mum, sister and I had to wait outside while Dad got the drinks. Mind you, that was also a time when "Gentlemen only" bars were common. It's right that the rules have been relaxed somewhat, but pubs are not really innately child-friendly places, and it should not be regarded as abnormal for a pub to bar kids.
I've been in the Lower Red Lion once or twice, as it's in St Albans, which I often visit. I'll make a point of visiting it next time I'm over there.