Go to the Kittery Trading Post. Do not go up to the top floor with a credit card or you will be sorry!!!!
Be sure to hit a lobster pound or two if you get a chance. They are little roadside stands where you can get a couple lobsters, fries and sodas for a $20 bill.
LL Bean is nice but very PC. Plenty of factory outlets around for the Mrs.
Be sure to go fishing on a party boat.
Last time we went, we went whale watching and it was awesome!!!!!!!! I'm not sure how many whales you see in Oklahoma but when one rolls about 30 yards from the ship, it freakin amazing! Definately something your daughter will never forget.
Maine can be very chilly in September so bring some sweatshirts. The cool thing is that you will be past tourist season and get some great room rates.