Can I travel from Eastport, ME to New brunswick Canada?

We are planning a family road trip from TN and was thinking it would be fun to go to Deer island. I also want to drive the "Fundy Coastal". Is it possible to leave Eastport via ferry to Deer island. Then go to say St. George by ferry later?? Thanks so much for any info you can provide... (P.S.) Where would customs be during this route???

You can get from Eastport to Deer Island by ferry but I don't think that you'll be able to get to St. George unless there's another ferry from Deer Island. It appears that you'll have to go back and drive around. As for Customs, I would expect that you would clear either getting on the ferry or getting off, whichever way you are going (to or fro).