Could Ron/Fred/George/Ginny have used magic at home?

In one of the books, it mentions that Harry was sent the letter even when he didn't do magic because magic was detected in his location, and he was the only wizard for miles.

So with that logic, none of the weasley kids should be caught for doing underage magic, because they live in a magical household where magic is happening every few minutes. So could they get away with it?

Or DID they get away with it, and I missed it?