Statistics Probability

A husband and his pregnant wife go to the doctor for an ultrasound. The husband is hoping for a son. The doctor tells them that the mother-to-be is actually pregnant with quadruplets! The father-to-be, still in shock, asks if that means that the odds are good that he will get a son.

Assuming that the quadruplets aren't identical (so each child has a 50-50 chance of being a boy, and all are independent of one another), is the father right? What's the probability of at least one of the children being a boy? (Hint: Compute the probability that all are girls)