Cape Ann - Isle of Shoals or York Harbor (entrance on a slack or near slack tide) - Portland - Boothbay - Hog Island - Tennants Harbor - Rockland. Most are easy days. There are many, many other nice places to stop between Portland and Rockland.
If you're concerned about lobbie pots, don't come to ME. They're everywhere. Just stay sharp and avoid them if you can. Be especially vigilant around high tide as some pots will be just below the water's surface.
A wet suit and a sharp knife might come in handy.
Fog's the other big worry. If the boat has radar, GPS and a chart plotter you can move around at slow speed without much difficulty. Stay vigilant.
Radar and GPS is good if you're fast with your chart work. Radar makes everything much easier. Without it, you need to go really slow with ears wide open and a look out on the bow fog horn in hand.
Have fun. Maine's a beautiful place when you can see it.