Here's what I would do.
Leave Gorham, NH, head for Fredricton, NB from there to Saint John NB, (reversing falls). Take ferry across to Digby, Nova Scotia, ride route 8 to Liverpool, N.S. then go left to Lunenburg, NS (scenic village, beuatiful place), carry on to Peggy's Cove,(lighthouse, tourist attraction) then on to Halifax, NS to the Lower Deck bar and restaurant on the water front in Halifax (www.lowerdeck.ca
From Halifax I would go up to and around the Cabot Trail, counterclockwise. This puts you on the "cliff lane" but you will love it.
Coming off the Cabot Trail head west toward New Glasgow, Truro and Amhearst NS and to the Confederation Bridge (conferderationbridge.com). If it open (wind closes it) take that over to PEI and visit the 'Anne of Green Gables" tourist attraction then back over the bridge and continue west back through NS and NB to Quebec. On your way past Amherst and Sackville, in N.B check out the tides on the Bay of Fundy, that is really cool.
It is a long way around the Gaspe Peninsula, beautiful but a long way around. I would cut across N.B. to Campellton then into Quebec and down the south shore of the St. Lawrence to Quebec City. Stop in and see the old world charm of old Quebec City, visit the Chateau Frontenac and wander the cobblestone streets. Great food, wine and jazz in Quebec City. From there i would continue down the south shore then head south to skirt Montreal and head back to the US in upstate N.Y.
then I would go to Lake Placid and across the the bottom of Lake Ontario to Buffalo and see Niagra Falls, N.Y and cross back into Canada to see it from that side. You can continue along the north shore of Lake Erie and follow it down to Windsor and take the Ambassador Bridge into Detroit. From there you can follow I-75 south and superslab your way back to Texas.
It would take me at least a week to do this trip from Gorham up through NB, P.E.I, NS, QC and then back to New York State. I've only touched on a few of the highlights, there are many more things to see and do in the Canadian Maritimes but those are the ones I would hit for sure.
Also surf the internet for Lobster Suppers in P.E.I. and New Brunswick before you go. When I was a kid the local service clubs would put these on all summer long. You sat down at long tables in local halls or churches and ate lobster with tourists from all over the world.
Have fun and take pictures and video. I know you will enjoy the trip.
Troy aka Calgaryglide