I'm 13 and I know that "suck" could be considered an adult-oriented word. But even so I don't think that it's Kelly's point of view or message in this song.
Let me just say, I think Kelly Clarkson has gone to the dogs. Literally. Her last cd was horrible, and while I think that this song is a LITTLE better, it still doesn't cut the "Breakaway" standards she set for herself back in the beginning when her songs were actually clean and good for all ages!!!!! And also, the title:my life would suck without you. The origins of "suck" are not good, and so you probably don't want little kids singing it nonstop, because its every other song on the radio!