Other people's moms

So, swim lessons at the neighborhood pool have begun, and it has been a very good thing. Jacob gets to swim with other kids, I get to chat with other moms, we all get some sun and some exercise and go home happy. But there is this one family whose kids are, frankly, extremely bratty. The first day we pulled up to the pool, they came out and said to Jacob, loudly and in his face, "You can't go in there, you don't have any shoes on!" Jacob is sort of opposed to footwear of any kind, and I had already told him he didn't have to wear shoes at the pool. (We have to pick our battles, ladies.) He looked at me for some sort of confirmation of this new rule, and I gently said, "It's ok, Jacob. Guys, he'll be fine." Jacob looked back at these kids, and they kept saying, again, up and yelling in his face, "Nunh-uh, he can't go swimming. You can't go swimming! You have to go home!" Jacob was seriously close to tears, and he hid behind me and sadly said, "Mommy, they said I can't take swimming lessons! Do we have to go home?" Now, this is not the only time they have done something like this. They are, like I said, pushy, bossy, thug-like little monsters. Their mother, bless her, does nothing about their behavior. She calmly sits by and lets it happen. She never says a word. And it's driving me bananas. Do I say something to her? Do I clue her in that her children should be nicknamed "BratSpawn?" (If I did say something, I probably would come up with something more polite than "BratSpawn", but it has a nice ring to it, don't you think?) Or do I just correct the kids myself whenever they send my 3 year old to me in tears because they refuse to let him on the steps of the pool for whatever evil reason they have come up with at the time? We still go to the pool, and we sort of just ignore those kids or avoid them when we can. But when Jacob gets up into one of their faces and shoots him in the eye with his watergun, you won't hear me complaining.