Well, it depends what you want to do.
If you want to check out touristy places you must visit the world most photographed light house in Peggy's Cove about 30 minutes south of Halifax. Then visit the historic town of Lunenburg as you continue south. Many photography workshops have passed through or have been located out of Lunenburg. Take the 2 lane road from Peggy's Cove to Lunenburg as it is about 1000 times more scenic than the 4 lane highway.
If you can get up to Cape Breton National park you surely will be in for one heck of a treat. Especially in October. I would also recomend if you have time to visit Prince Edward Island which is about 3 hours east of Halifax. While you are in that vicinty you can check out Fundy National Park maybe 1 hour and 40 minutes south of the island.
These are all places I visit many times each year. There are other smaller provincial parks and off the beaten path type places you can visit, contact me if you need more information.