Car Free Sunday Overijse

Have checked the Overijse website but I don't see anything about car-free Sunday.  We live right near the lake on the Genval side but as we have guests that weekend I'm wondering if they can park their car on the Overijse side and that way be free to leave when they want to.

Anyone know if Overijse participates and if so the map of the area concerned?

Cheers