It is wonderful that you are planning so far ahead. You only have six full days, and yes, what you have outlined is too ambitious.
Before deciding where to go you should get a good feel for our different regions and what they have to offer. You also need to decide what things are most important for you to see and do. Study this website and send away for your map and guide: www.novascotia.com/en/home/default.aspx
Read some of the trip reports from others who have visited Nova Scotia here. They will give you some ideas of what is possible with the time you have: tripadvisor.ca/Travel-g154967-c157554/Nova-S…
Also check other current threads on this Nova Scotia forum.
You will probably have to limit yourselves to Cape Breton and one or two other places. As kayakdover says the best place to experience the tides is the Advocate Harbour area. You would likely want to spent at least two nights there which would only give one day to explore. You would be able to see the tides, visit Cape D'Or and possibly the fossil cliffs and museum in Joggins and the fossil museum in Parrsboro (two different geological periods). If you want an area that is untouristy and full of nature, this is it.
If you only want to go to Wolfville to see the tides then I would give it a miss. If you are interested in wineries then it is worth going.
You arrive in late afternoon and it is probably not worthwhile going to Halifax. You would not have time to see much. However it is a wonderful city with a great waterfront. If visiting rural areas with great scenery is more important than I would start my trip by heading towards Cape Breton.
For Cape Breton you can drive around the Cabot Trail in one day but you would not have time for more than a short hike. The day you go whale watching you may also be able to hike the wonderful Skyline Trail.
You should consider visiting the Fortress at Louisbourg, the Bell Museum and the Highland Village Museum. That means spending three days in Cape Breton.
Of course Lunenburg, Mahone Bay and Peggy's Cove are must sees and you can see them in one day if that is all the time you have.
Here is a possible route to take. Check the driving times carefully. They are in best conditions with no traffic, construction or stops. http://bit.ly/15NneZj
night 1: Antigonish?
night 2: Baddeck - Bell museum, Highland Village Museum,
night 3: Ingonish visit Louisbourg in the morning and drive to Ingonish or Pleasant Bay.
night 4 Mabou or further after whale watching out of Pleasant Bay or Cheticamp
night 5 Advocate Harbour
night 6 Advocate Harbour
night 7 Lunenburg?
The above is still quite rushed but doable I think.
CAPE BRETON for others
Cabot Trail Review and information