Keeping job after baby is born

I'm trying to come up with a plan to propose to my boss that will let me keep a courier job twice a week after baby is born. 2 other couriers bring their toddlers/young kids but none have a baby. It involves a half hour of walking in and out of businesses, picking things up then taking a ferry and back. I have no worries about the ferry just the businesses. I was hoping to wear the baby in a backpack or sling. Any advice on this? I do have seniority at the company and my boss loves me- however I never see him and he doesn't know I'm pregnant yet. Do any of you have suggestions? I would appreciate any advice!