It all depends on where you are starting from and what you want to do.

If you start your first day somewhere along the Fundy Shore, then 2 days is probably doable for seeing the Bay of Fundy and Hopewell Cape, although you'll not be able to see everything (NB & NS).

Where did you plan to spend the second night? Halifax is about 3.5-4 hours from Hopewell. If that's where you spend the second night of your trip, then Day 3 would be really full (3 hours just for the driving, plus the time for sightseeing). Whether that is too much for 1 day would depend on what you want to see, but I suspect other posters here will tell you it's too much.

If you DON'T spend Night 2 around Halifax, then Day 3 is impossible.

Depending on the route, Liverpool to Brier Island will run 4.5-5.5 hours of driving. Any sightseeing would be in addition to that.

What do you want to do on Brier Island? I doubt you can fit a whale watch into your schedule. You'd really be pushing it to get to BI in time for an afternoon sailing, and you might not make the ferry if you do a morning whale watch the next day and get delayed.

Brier Island to Digby is about 2-2.5 hours, from what I understand. So, depending on what you want to do that day (other than a whale watch), it is very doable in time to make the ferry at 16:00. If you want to take the morning ferry, I would not stay on Brier Island the night before.

OK...thanks for the reply...we'll be starting the 1st day at the Bay of Fundy, we were planning to stay somewhere around Halifax for the 2nd night, then do Luneburg, Mahone Bay and Peggys cove, stay around there (somewhere!) then drive to Liverpool and Brier Island...we did want to do whale watching there (or is there somewhere better?) maybe we need to stay there 2 days before we take off to digby...We're not sure what sights we want to see yet...any suggestions would be appreciated! thanks

You'll be busy but it's probably doable although I'll add a few comments. 2 full days for Fundy Shore is OK - make sure you include Alma/Fundy National Park and Hopewell Rocks which you do specifically mention. Personally I would overnight in Alma because the tides are very dramatic there and an overnight will allow you to contrast the vast difference between low and high tide.

I would stay right in Halifax the 2nd night as it's a very nice city with a compact downtown and vibrant Harbour District to spend your evening in. Mahone Bay, Peggy's Cove and Lunenburg is quite a bit for one day, although the Peggy's Cove stop can be brief for photos of the picturesque fishing cove and then the granite ocean shoreline and Lighthouse. Then on to Mahone Bay for a walkabout and lunch, and maybe finish off (and spend the night?) in Lunenburg with another walkabout and dinner.

If you have time (which seems unlikely) - exploring the shoreline roads along the South Shore "Lighthouse Route" is immensely nicer than staying on the highway and larger roads.

Book your whale tour out of Brier Island well in advance. Grand Manan Island off New Brunswick is also famous for whale tours but, requiring a ferry crossing, that might be equally or more difficult to fit in. There are whale tours from other locations but my impression is that the Brier and Grand Manan ones are particularly known for quality (we've done Grand Manan and were thrilled). Both Islands are very laid back and have some nice dramatic scenery (e.g. basalt cliffs).

Too bad you don't have time to get up to Cape Breton, which is spectacular.

doable but rushed.