I have always recognized that I need to be the most patient and generous to fellow anglers when they are children, and it does really grind my gears when I see others not extending the same courtesy. All the same, I learned years ago to take the pre-judgments of others with a grain of salt, and to give others a chance on my own. I don't know if it was only one day or incident that made your friend feel like they should warn you of fishing at this location, but I know I would have missed many fine days of fishing with some wonderful fellow anglers if I had listened to everyone else's warnings about fishing at certain popular locations. My advice is to check it out for yourself first, maybe without the kids.
Whenever I take more kids fishing than just my daughter (such as her entire Girl Scout troop), I arrive early to set up and politely warn the other anglers of the chaos that is about to ensue at that particular location. Some pack up and move, others stay for the show and even are willing to help out!