Educate yourself before making any heart-wrenching decisions. Research your pet's breed and gather opinions from professionals to try to understand what's behind its behavior. It may be that a few simple changes in how you handle the pet will make a difference. Medication may help, as well.
Consult more than one trainer, if you have the resources to do so. All trainers have different techniques for behavior modification and discipline.
A shelter may not be the best solution. "An aggressive pet views the new baby as another animal, so putting it in a high-stress environment with many other animals could be very hard on your pet," says Yohannan.
Try finding a friend with whom your pet is familiar and who can provide an environment free of the triggers (kids, other animals, etc.) that set your pet off.
Don't let anyone bully you into doing something you're not comfortable with or make you feel guilty about whatever you decide.