Welcome to Flyertalk.
With Christmas Eve being the feast of the seven fishes in many cultures, and Portland being so closely tied to seafood, it's probably going to be hard to get a non seafood Christmas Eve dinner in Portland.
This page
http://www.pressherald.com/life/food...010-12-15.html
Lists what was open last year on Christmas Eve and Christmas Day, it could be a starting point to see if they are open this year too.