Do you feel the shaking in the steering wheel -- does it oscillate the steering wheel back and forth? If not, your rear brake rotors/drums may be out of round. If it does shake the wheel, get back to the front rotors and check them for being out of round. Even new rotors can be out of round.
A "loose front end" will not cause a rhythmic shaking of the wheel or vehicle upon brake application. Not to say your front end shouldn't be checked if you feel something is not right. Just to saying you should concentrate still on the rotors.