Hi Amy-
My kids are 20 months apart and I have been through the gambit of strollers. Honestly, I feel that today you can probably have one stroller for all your activities (running, walking, shopping, zoo, errands, etc.) My suggestion would be the BOB Double Revolution. It is light, fits through a standard doorway, has an independant front wheel and able to steer with two fingers. I would also suggest the Baby Jogger Double Urban. Although if you are any kind of runner or power walker, you would be thrilled with the BOB. I agree with Michelle, the best way to purchase this stroller is through www.Joggermom.com. She has the best service and probably most knowledgeable stroller mom I have ever met. Plus she has great extras, usually in stock. When you baby is born, she also had the infant carrier bar which attached perfectly to the BOB. I have had a Baby Jogger Twinner (2x), Schwinn Double, Baby Trend Double and Graco double. My absolure favorite is the BOB.
I hope this helps. Good luck and Congratulations.