I think we've all been there. I went for a practice on Saturday with a friend and we have similar things - flash photography, kids diving on the approach, etc, etc. Unfortunately, that is the risk you take with open bowling.
I have seen a small girl come within inches of being badly hurt after she followed a bowler up the approach behind him. Bowler was unaware and has a big back swing. It was very scary to watch. I've also had small kids come racing round corners and charging into me before. I am not an enourmous girl myself and when I'm carrying 4-6 15lb bowling balls, I am physically unable to move that quickly. It's not nice when they charge into you and make connection with something hard and start crying - it makes me feel horrible. But, it's not our fault.
HOWEVER, from my experiences, if you actually go and ask the parents nicely, they'll often make a real effort. I think it is very reasonable that we expect kids not to dive on the approaches and run around, however, with regards to them wandering over to our approaches, not giving way and 15 of them being on the approach - well, that's not rudeness, just ignorance and often if you explain or ask nicely, you won't have any problems.