Be sure and have beer and Mussels in the old quarter , plenty of restaurants to choose from .There`s a mussels festival at some time ( ? ) where each restaurant competes to see who can have the largest pile of mussel shells outside their door.
There is also a very famous old chocolateir called Chez Meert which is just off the big square , you can drink hot chocolate by the half pint out of silver tankards with cakes . Its a really beautiful place that looks like it hasn`t changed in centuries , but boy is it rich, leave plenty of time before dinner.
have fun.......