What exercise regiment would work best for me?

I gave birth to my son 6 months ago. Before I became pregnant I weighed 127 I now weigh 172. I am unhappy with my weight, and overall physical appearance. I would like to join a gym in my area but I am interested in group activities due to lack of self motivation. I am slightly overwhelmed with all of the choices set out in front of me. I don't want to build muscle I just desperately want to shed the baby weight and trim all those unsightly areas. I know nothing will be super fast or super easy, I just need to be pointed in the right direction. Pilates, cardio, yoga, aerobics, dance, cycling cles????? Me head is spinning.