I'm sorry, but if you have a kid that for some awful reason, you've given an iPhone, and they are looking up dirty (F$#K!) in a dictionary app, and they are not of the age when they are hearing it on a daily basis from their peers anyway (11) then:
1. You have already failed as a parent. Please have your children report to the nearest hospital in Nebraska. Do not bring them there, they can safely traverse the distance- you cannot. A major meth incident is about to go down, and an infant can probably dodge strangers better than bullets. At least you can be confident that in 20 years, they'll have the knowledge and resources to ensure you don't get eaten by rabid animals. And frankly, you'll probably need the help.
or....
2. You are an uber-geek, your kids are probably uber-geeks. There's nothing you can do about it. Send them on the pilgrimage to Nebraska, and they'll end up starting a colony on Mars. Probably best to just let it go. They can handle a few dirty words- and still school the heck out of their peers. Congratulations- you'll never have to take the blame for a serial killer, and you'll be happy to take the credit when they nab the Nobel Prize.
So come on people, let's let evolution take its course. One dictionary at a time!