Thanks, Jean-Marc. I'd suggest late June and July, maybe early-mid August, if your calendar allows that.
A few notes:
1) Take your rain gear. Some years back, I was scanning a motorcycle ride in Nova Scotia, and looked at the very helpful guide that the province produces. I was esp interested in the Annapolis Valley, which runs parallel to the Fundy Shore. Said the guide, "Take your rain gear. It might not rain when you are touring, but that would be unusual."
2) I sketched out a route on Komoot for the tour I outlined above. Happy to share that with you if that's useful. Suggest we do so via PM or regular email.
3) The route I described above does not include Halifax or the area south of Halifax towards Peggy's Cove and Lunenburg, nor does it include Yarmouth and the Annapolis Valley on the Fundy Shore. I'd suggest including at least some of that, if your time allows. (Reason I excluded those areas is that I've visited them several times.)
4) My route doesn't include Prince Edward island, either -- again, have visited it several times. It is ideal cycling country, though.
5) One of the reasons I enjoy cycling in Atlantic Canada is that the distances between settlements are usually more manageable than in many other parts of this vast country.
6) I've done less cycling in New Brunswick, hence my interest in cycling along the NB shore of the Gulf of St Lawrence. (I had chosen Bathurst, NB, as my starting point.)
7) If your time allows, the Gaspé peninsula of Québec is a fabulous ride as well. (That's the easternmost part of the southern shore of the St Lawrence, the bit that is just north of NB & sticks out like a thumb into the Gulf.) In 2010 I rode that clockwise from Matapédia in its SW corner with a friend from Manhattan. He is well-travelled, but said, "John, I've never been anywhere quite like this." That journey took us about 9 days. I don't have a journal, but I do have a file with out route, stops, etc.
Cheers, John
And a late PS, Jean-Marc: If you're in those parts, I'd urge you to visit Québec City. No place quite like it, in North America at least. Ancient walls, old town and citadel, A-grade food and drink, jazz on the promenade at night overlooking the big river...