I live in Charlottetown and I love to eat in restaurants. I am assuming you will be two adults.... and it's amazing how many good restaurants we have for the size of our city...
Fine Dining and Good Atmosphere
Pilot House
Restaurant at the Prince Edward Hotel
Restaurant at the Charlottetown hotel
(very good restaurants for hotels)
Good home cooking and good atmosphere and good prices
Papa Joe's
Swiss Chalet (the best one I have ever eaten at - I think it's the PEI potatoes)
Angels
Shaddy's (fabulous Lebanese food)
and my favourite Cedars (you have to try their house chicken)
For fabulous coffee and desserts
Beanz - University Avenue
Real good food - pub-like
Merchantman Pub (across from Prince Edward Hotel) - Queen STreet
Outside of Charlottetown
Unfortunately I haven't tried many restaurants outside of Charlottetown and Summerside. Dining in Summerside is poor except that I have heard of a new place called Heritage Pub that is supposed to be really good.
In New Glasgow is the PEI Preserve company that has a fabulous restaurant called Cafe on the Clyde. You you can get take out strawberry shortcake - ask to have it with Creme de Grand Manier ice cream - ahhhhh - can't wait for strawberry season...
http://www.preservecompany.com/index.cfm?do=about_dining
Feel free to ask me any questions and I agree with a previous post on beaches. We are surrounded by beaches - rent a car and just wander around. Put Victoria by the Sea on your list of must visits.