Alright, after more painful searching on AT&T's disorganized site, I found the answer to my own question.
In case anybody else is curious, this is the answer:
Question:
Does the early termination fee apply to each line on FamilyTalk or just to the plan itself? Answer:
Each phone on your FamilyTalk account has its own contract. If you cancel your service with us before the end of your contract term, you will pay an Early Termination Fee (ETF) for each wireless phone number associated with the account.
New and renewing AT&T wireless customers who entered into a 1- or 2-year Service Commitment prior to June 1, 2010, have an Early Termination Fee (ETF) of $175 less $5 for each full month of Service Commitment completed.
New and renewing AT&T wireless customers who enter into a 1- or 2-year Service Commitment on or after June 1, 2010, and include certain
specified equipment, have an ETF of $325 less $10 for each full month of Service Commitment completed. Otherwise the ETF is $150 less $4 for each full month of Service Commitment competed.