Yes cps will take your kids if you fail the first drug test. They tested my son and his girlfriend for drugs ans when the test came back positive they came to the house with the sheriff and took the kids.
We can't tell without knowing what state you're in. A safe bet however, is "at least until you DO pass a test, and then some." If they take them at all; I have to think a single bad pisstest isn't always going to get your kids taken - the State really doesn't WANT your kids.