First, really think about whether or not you should bring your kids. That's not a good idea in many ways. Dogs can get excited about food when kids squeal or move quickly.
You should bring people food to the dog park if you want to see a bunch of dogs sitting and looking at a person.
Very, very bad. People who bring a baggie of treats to share probably mean well, but it's rude to feed someone else's dog without their permission.
Everyone knows everything, right? Not really. But some people at dog parks think they know everything just because they have a dog.
These problems don't just happen at dog parks; many of us are guilty of blaming the breed instead of the dog for certain habits.
I've seen dogs that don't want to play and are trying really hard to tell their owner that they just want to sit there or leave get told over and over to go play.