It definitely takes some getting used to, even for people from NS.
So you can take the bridge to PEI (no payment to get on the island and we love the shops at Gateway Village), from which you'll be a short hop to Summerside. From either the bridge or Summerside, it's maybe an hour to Cavendish (stopping for ice cream along the way). From the bridge to Charlottetown is about an hour, maybe. I always assume it will take me at least an hour to get from Charlottetown to the ferry, because somehow I always end up behind a slow moving farm vehicle.
It used to be that everyone took the bridge (when it was first built) but many people are taking the ferry again. So the pre-arranged boarding pass is definitely worth it -- it can save more than an hour of waiting.
Antigonish is not too far from where the ferry lands at Pictou, so you won't really even have to stop along the way.