AT&T Family Plan contract/handset gymnastics

I realize this probably belongs in the carrier forum, but it doesn't look like anyone reads that board..so....

Family Plan customer since 2008, FAN Discount via employer.
Still under unlimited (grand fathered)
3 lines
3 iPhone 4S still in contract

One of the handsets took a bath in a pool.

On 1 of my lines/handsets the ETF is 145.00 (6 1/2 mo. till contract end)

Question: What's my cheapest route to a new handset where I still end up with 3 lines/3 phones?
...and still keep unlimited data...of course

im willing to pay the 145.00 ETF...it's just the steps after that have me confused.

thanks in advance smart people...