I'd ask. I asked one of my parents what their plans were for summer and turns out, they planned on giving notice (dcm was changing to casual employment and grandma doesn't charge based on enrolment ). The extra time (outside notice) allowed me to start advertising earlier than if I hadn't asked.

If anything it would give you time to advertise or to offer them a lower rate if you choose to do so. If it were me I don't think you asking would put the idea into my head. Plus I don't know about Toronto, but daycare centres usually have a huge wait list over here so if he isn't on a list by now, I doubt he'd get on it by September.