Kid-Appropriate Language?

As an occasional babysitter for numerous families, I have come across every method of parenting you can imagine. I am more than happy to adhere to the rules of different parents; THEIR kids are the ones I am caring for, after all. The one thing I wish they could all come to agreement on is the kind of language I am permitted to use around their kids and that their kids are permitted to use around me. It's more confusing than the conundrum debating whether it was the chicken or the egg that first made its appearance to try and keep straight when I can say "crap" and when it is considered the worst swear word known to man. I did not know it was possible to be opposed to "crap" until quite recently. 

The easiest kids to babysit are the ten-year-olds around whom I can say, literally, any swear word I want and they can reciprocate. Getting angry during video games is so much more simple when my mental filter isn't making me say ridiculous words like "shoot" and "drat" and "oh, fudge!". However, there is one catch to my sailor speech around these kids- I cannot use foul language in a manner that can be construed as directly insulting to the kids. That is kind of a no-brainer to me. I feel like anyone who calls a ten-year-old a "f***ing a**hole" is just asking to be targeted by social services. 

Thankfully, I can put up and tear down my foul-language barrier quite easily. Even some of my friends are more sensitive to certain derogatory words than others. It varies by nationality, too. For example, J.K. Rowling throws the "C word" around in her book The Casual Vacancy like it is no big deal whatsoever, an act which I imagine would shock most people from the United States. I learned that the "C word" is common vocabulary in Canada and Australia as well. 

Having the radio on around kids is another huge roll of the dice. Some stations bleep out the word "ass" whereas some leave the foulest of foul language perfectly in tact. I thought there were regulations on that kind of thing. If the kids are in the car and one or two swear words slips through the censorship cracks, I like to hope it is not the complete and total end of the world. I'm sure that people swore like sailors around me as a kid all the time in restaurants and other public places and I never registered it in my little brain. I don't consider myself permanently damaged, anyway.