Just returned from Portland, ME
Quick post to highly recommend the two places we ate with our picky 3 year old:
Flatbread Pizza - GREAT location, GREAT atmosphere and really really good salads and pizza. I wish they would open one here in the Midwest. It is organic and local and close to the Ferry terminal, which means there is lots to do with cranky little ones while you wait for a table. Yum!
O'Naturals - again, GREAT location, Great atmosphere and I love their breakfast sandwiches. We had a flatbready kind of crust with egg, bacon, cheddar (just a sprinkle) and tomato. There is a nice place for the kids to play there - very safe and entertaining train table/dollhouse/books galore. It is just up the hill from all the great little shops in the Old Port area.
Sorry I can't give addresses, but in Portland, you go until you find it. What a great town.
Portland, Maine is my hometown, and I can tell you that the best pizza in town, and probably the best I've ever had anywhere, is Pizza Joint on Forest Avenue. I haven't lived in Portland since 1983, when Pizza Joint was way out by Morrill's Corner, but in 2001 I went back and got a pizza from their new location, near USM, and it was as good as I remember.