In a word, YES! Although your toddler will have her days of wanting to run around the mall or run ahead of you outside, you will want the double for a couple of reasons:
*When you are shopping you'll definitely use the extra room for holding your bags.
*You'll have days where your toddler will want to run away and you need to strap her in so you can concentrate on what you're doing or the baby.
*They will both fall asleep on you and you'll need a place for them to sleep while you're out. I guarantee it.
If you currently have a one seater stroller, keep it. You'll use that too.
I live in Medina so I know it's not quick to get home from shopping to put the kids down. You WILL let them sleep in the stroller so you have minutes of peace and quiet to shop or eat or whatever. You'll probably also find yourself pushing them around longer than necessary just to have the quiet time for mom!!!
One other reason to have the double stroller: We know men aren't the best at multitasking. So when dad takes the kids out so you can accomplish something at home (sleep, clean, whatever) he'll appreciate the double stroller then! Convince him that you're doing this for HIM. :)
~RachaelB