So I stopped (shocking, I know) and tried to apologize, but it's hard to do that while laughing. I believe Amanda's words were, "Gee, Mom, thanks a LOT."
Amanda is now paranoid, and rightfully so, that I'll drive off without her whenever we go to pick up Henry. So now as she exits the car, she looks at me and says, "Don't drive off without me." I promise not to, only to hear her sister in the backseat start chanting, "Drive a-way! Drive a-way!"
Pretty sure this will end up being one of those memories that Amanda recalls in counseling someday.