"Is there anywhere they are allowed to go in groups, or are they beyond the pale everywhere?"
There are loads of places where they can go (not least as confirmed by SurbitonMummy as available right in the area of this incident).
There are lots of different types of cafes, bars and restaurants. Some are very family friendly, some are OK, some aren't, and some restrict their clientele.
Unless you want all kinds of eateries to be pretty much the same, then that sort of range is going to exist. I like the diversity; and went to (sometimes) noisy family friendly places when DC were small, very quiet places when I had a hangover, very grown up and plush places for an important date etc