Do they like mussels? Mussels and fries is a big specialty (
Moules frites). Three are a lot of places that serve that in the downtown/old city part. And good little bistros all over.
There are street vendors selling Belgian waffles, usually the Liege style, which are very different from what we think of as a Belgian waffle in the US... but very good.
The chocolates are great.
I vaguely remember drinking a lot of interesting beer last time I was there... but the memories, while pleasant, are fuzzy.