WOW! We had better pull over & get out of your way.
Also headed to Nova Scotia & Newfoundland this year. We don't make reservations most of the time unless for a special event but I do some research so we are not traveling blind.
The problem with Maine & further north is that spring comes late. Maine CGs don't start opening till early May, & even then check first. Getting into NB & NS they open even later. Many open mid May to late May. Some are well into June before they open.
Check climate history records too so you know what to expect.
Leaving FL late April you should be OK. We leave home, Bermuda, early April for the Chesapeake Bay area where our rig is stored but we will be almost 3 weeks kicking around there enjoying some boatyard hospitality & doing the annual major truck & trailer service, waxing etc. before making a slow passage north aiming for Calais, ME around 2nd week of May.
Enjoy the ride. 3rd time in the area for us but the first 2 trips were fall trips where we had CGs closing behind us.
Oh, forgot one very important thing. The CDN$ is very low right now. We bought CDN$ today @ .65USD$ Is it going lower? Don't know. Will it rebound? Don't know that either. Many places like cash, especially if a discount is offered so you might think about buying some CDN$ sooner rather than later.