Appointments+: Adding family members?

I love the app and plugins! But I need to add the ability to have multiple family members assigned to appointments for a given account.

Example:
Mom has an account and schedules an appointment for herself. Great! Now she wants to schedule another appointment for Johnny, then one more for Jane. So we need to allow her to add multiple names and then choose one from a drop-down menu when setting up an appointment.

Solution?:
I was thinking I could use and rename multiple shipping address fields from MarketPress, but as far as I know, it isn't possible to use shipping addresses with Appointments+ (?)

What's the best way to achieve this?

Thanks in advance!

EDIT: Family members don't necessarily need to be able to schedule the same appointment slot.