I haven't been in these area, except for around Bar Harbor- and plenty of people can spend 4-5 days just there. Like sunrise in Acadia then kayaking and touring the downtown area of Southwest harbor could be a full day.
I'd stop for that first night in Portsmouth and just walk around the harbor after dinner- spend time there on a weekend getaway.
I'd probably flip Cape Breton and spend more time vs. PEI because of the National Park.
All in all, it sounds like a great trip, and you'll probably be setting up camp in half the time after just a few days. Any place you go that time of year will have sunshine and cool nights, with leaves changing, and fewer crowds with kids in school. Enjoy the views and solitude!
