I know this will probably evoke all sorts of comments, but we just drove to the East Coast from PEI. Our usual route would have been very similar to the OP's, but while playing around with Google Maps one evening, I discovered that there was very little time or mileage difference if I used a route that went north of Maine, passing just east of Quebec and Montreal and came back into the US in western NY. So that's the route we used.
IMHO it was a great way to go. Since the weather was a bit warmer we even stopped and had a couple of days in Old Quebec, one of our favorite cities in this continent. Once we crossed into the US near Massena NY we proceeded down the I-81 corridor to the PA-MD-VA area. Compared to anywhere along the US East Coast, traffic on the Canadian part of the route was light even near Montreal, since we were across the river from the city. And that far north I-81 isn't terribly busy either.
All in all, we thought it was a great route and will use it again next spring when we return to PEI.