Summer months low enrolment.

[torontokids]

So your concern is that the kids won't have anyone to play with? What about your own kids? It sounds like this is more your concern then the parents? I would just turn it around as a positive. E.g. This will give us lot's of opportunities for 1:1 time and give us the chance to do a lot of fun activities that would be difficult to do with a large group. Talk about your plans to visit parks etc often so there will be lot's of opportunities to play with lot's of kids. I wouldn't worry about it. If the mom asks about the empty spots mention you are waiting to fill the spot until Sept for the above reasons.