Absolutely, yes! With DoorDash, you are your boss. You can have someone in your vehicle as you make deliveries. This can be a friend, child, or spouse. DoorDash does not mind if their presence does not interfere with your work.
DoorDash drivers are considered independent contractors. This means they are free to conduct themselves in any manner if they do not expose DoorDash to any liability. As such, you can have someone accompany you on your deliveries, especially when you are making deliveries at a late hour.
However, you and you alone make the delivery. It is against DoorDash rules for your friend, spouse, or child to use your account or make deliveries for you. That could get your account deactivated.
Some customers and merchants will report your account if someone else shows up to pick up or make deliveries. Some drivers might get away with this if the other person is of the same gender.
Furthermore, it is not a great idea to bring little kids along when making deliveries. If your kid is old enough, they can keep you company or help with handling packages. However, only you should contact the customer.