I don't like breathing smoke while drinking, and really don't while doing critical tasting. That said, I don't recall a major problem in Belgium the times I've been there. Avoid the heavy crowded times if that's an issue, or choose seats accordingly. Not an ideal solution, but you play the hand you're dealt.
Sounds like a plan - it sounds like some of these places have designated non-smoking areas, but it's been my experience that they're just 'seats further away from the smoke.' I'm going to be there during the day with my boy and my wife which is why I'm concerned about smoke in the first place, but it sounds like it'll be alright. Thanks!
P.S. - as a French citizen it's actually part of my constitutional duty to complain about Belgium.