Hope you like eating no later than 6pm. Outside Halifax, the whole province shuts down at 8 (and Halifax at 9, lol). The Cabot Trail is beautiful if you're not stuck behind an RV, and Digby scallops are the best, but three days in NS will feel like a week and a half.
Noticed you didn't mention Calgary. Only reason to go there is the Stampede, but Banff is gorgeous.
As long as we're in Canada, if you've ever thought to yourself, "There's a few hours I'll never get back," that describes any time you spend in Thunder Bay.