Here is some information from a post I made yesterday on Trip Advisor:
It is easy to walk around the main parts of Halifax on your own. Almost everything of interest is along the waterfront, up Spring Garden Road to the Public Gardens or on Citadel Hill.
Here are some links:
This one seems very expensive: https://www.toursbylocals.com/Halifax-Historic-Private-Guide
Official Halifax information: https://discoverhalifaxns.com/ and https://discoverhalifaxns.com/plan/visitor-guide/
This is free but self guided: https://discoverhalifaxns.com/wp-content/uploads/2019/04/Leisure-Walking-Map-2019.pdf
You can make your own tour using this: https://www.gpsmycity.com/gps-tour-guides/halifax-552.html There is information in the site about each place.
This self guided tour may work for you and you can add or subtract places of interest; https://mywanderingvoyage.com/2017/08/20/explore-halifax-walking-tour/
These people may be able to do a walking tour: https://www.toursbylocals.com/Halifax-Tours?gclid=CjwKCAjwoMSWBhAdEiwAVJ2ndhouQATgmz5dS4fsdEX4cUGDB3_-1CKWEcEMU_dQlqUKCK7hfr2hyxoCrHAQAvD_BwE
Also check out Toms Port Guides
You need less than an hour to get to Peggy's Cove and if you get there before the tour busses you can have a pleasant short stay for a few minutes. Then follow the coastal roads to Mahone Bay. Just before you get there there is a wonderful view of the bay with three churches. Mahone Bay itself has shops and restaurants but I would push on to Lunenburg for lunch and a quick look around. Take the main road (103 back to Halifax.) Coastal Route Highway Return As you can see taking the coastal route and including Peggy's Cove and Mahone Bay may not be easily done in the time you have.
There are some boat tours out of Halifax Harbour but it is not a good place for whale watching.