I remember when I was a kid and this drove my parents insane. Mom, as a result, taught me that if you have dinner at any place labeling itself as "family", OR if it is before 7 p.m., just be prepared for brats. One time my husband and I went to a high end restaurant for an anniversary dinner ... and there were single-digit aged kids crawling under our table. Literally across our feet. Another time my husband actually went and tipped the wait staff extra because my young relatives were so horrid that we were embarrassed.
The flip side of that is once in awhile we go out someplace pricey and nice (not that they are mutually exclusive) and I've thought, oh, dog excrement. A table of young children next to me. Then been very pleasantly surprised. When that happens, I actually make a point of talking to one of the parents before we leave. "Your (appropriate child pronoun here) is very well behaved and had beautiful manners. I want you to know that we appreciate that." The bad experience is so much more universal for me that I can come home feeling shell-shocked. And it isn't just children who can be the problem. I've gone out and had to leave because a restaurant was so noisy ... the jukebox. I look around and I'm the child in the room, which is some heck of a note given that I'm in my mid 50s, husband in his early 60s. But the music that is blaring, I mean really, really, blaring is the choice of the waiters or kitchen help, because no paying customer has ever heard it.
By the way, several times when I've commented on children's good behavior, the parents told me they have "practice sessions" at home. This amuses me to no end, because we did as children as well. We practiced using china and crystal and silver. Place settings. Inside voice and conversation. We didn't do it every day, but we did it most holidays and winter Sundays. We'd each get a wine glass full of usually cream soda (heck, it looks just like champagne!). No cans, jars, or bottles on the table (yes, even catsup would go in a small bowl with a spoon).