Can't help you much with NS hidden gems or trails. We spent more of our time on Prince Edward Island, but can tell you that Peggy's Cove is a special place in NS. The road to there would be tight for a motor home, we were glad we had our toad.
The Bay of Fundy is awesome with the enormous tide fluctuation. We saw that from the NB side at Hopewell Rocks.
Children under 16 only need proof of US citizenship. You'll need to check the rules on passports. And check the rules for pets, too. Happy trails!
Bad decisions make great stories!