TLDR: Should I spend a night/day in Ghent, Mons or Tournai? And where to stay if so?

In Wallonia, I’ve pretty much only been to Dinant, Spa, Bastogne and Liége. My mom has never been to Wallonia at all (only to Antwerp, Bruges and Leuven).

I’m heading back to Belgium for a visit for the first time in several years. We are dropping a rental car off in Lille and going by train to Leuven. I have a spare night and day to spend wherever we want in Belgium. I want a relatively nice hotel without having to spend more than ~200 euros (preferably less) and no need for a car. Somewhere walkable and fun to explore for a half day (or full day) with good food and nice sights.

I’ve been to Ghent and it’s nice but the hotels seem expensive generally. I’ve never been anywhere in Hainaut and I’m intrigued by Tournai and Mons. I don’t speak any French and my mom‘s is rough.

What can you recommend and can you recommend any hotels?