It's a half hour from the airport to the port, the shuttle should drop you off no later than 2:00pm and then you will board. 6:40pm is way too late to board, you will be on a lot earlier.
No, but around the port there are a bunch, lles deux ponts, Bistro Le port etc. Look for Moules Mariniere with frites. Hank (Hlitner) might have a suggestion too.
I was with the Zaandam this summer in Charlottetown and I planned to have mussels for lunch in a local restaurant, but I saw the mussels being delivered and I waited and had them for dinner, delicious.