Lobster in Maine
George:
The Biddeford (B19), Sanford (SFM) and Portland (PWM) airports will all put you near lobster, but none have courtesy cars. You would be able to rent cars at all of them though, and it probably wouldn't run you more than $40. A couple weeks ago I flew to Laconia, NH to attend the NASCAR race out there, and the rental car only cost about that.
As far are great lobsters go, I highly recommend Bayley's Lobster Pound in Pine Point. It's right on the water and beside a great beach to walk on. Full disclosure, they are family, but they are also the best around. The best airport for Bayley's is Biddeford (3000' of pavement).
Depending on the day you come in, I may be able to give you a ride; though I will be pretty busy this week and this coming weekend.
Antony