the saint john to digby ferry does have the virtue that you would get to go to the "habitation" a recreation of the first permanent setlement in nova scotia and north of the spainish settlements. it was started in 1605. a great precursor for louisbourg(and it's louisbourg not lewisberg--with a silent s)
then drive up the lovely anapolis valley to halifax then on the way to cape breton you could stop at sherebroke in guysborough country which also has an historical recreation site by parks canada.
louisbourg is fabulous. it does attrack a lot of people in the summer so bookinga room in advance might be a good idea but you could get one in sydney a drive out there--it's a half hour drive.
going through new brunswick could get youto fete acadien with good timing --also nice, and if you had the time to drive up to the acadien pennisula there is a great summer baroque festival at lameque and miscou islands which has great beaches and good music.
i would highly recomend the habitation in old port royal. and look for local church suppers--some are advertised on line. many communities have summer church suppers of lobster salmon or strawberry short cake etc. they do advertize and try to get the tourists. they are great local fare and you help fix the church.