Short Answer: If you're traveling together, you will go together, regardless of your age.
I've repeatedly flown into the US from overseas, most recently last month. My family is mixed US passport and Green Card, and we don't have the same last name. Regardless, we've always been processed with the automated machines.
If there's someone with a US passport in the group, and everyone else has the required visa, then you all go straight through the automated system. You can choose your preferred language for the process at the kiosk. A non-US citizen will have to submit to a finger print scan at the machine, everyone must answer questions about their trip, and everyone will be photographed. At the end, each person has a printed "receipt" to carry, and eventually give to a customs agent.
You interact with a human afterwards, but almost everything is done by machine.
There's a long queue beforehand, so use the restroom or fill your water bottle immediately after you leave the plane. We've stood in line up to 40 minutes.