I would like to know if it's long before filling our spots, if someone knows if TO requires a permission or not?
What do you mean by this?

By Ontario law, we're allowed to have 5 children under the age of 10 years, not including your own.

It all depends on the hours you keep. Consider this: Say I have 5 children - not school age. Say 2 of them are within the hours of 9-4. And then I have 2 b/a school kids - I can have them in the a.m. when they get on the bus at 8:25, and then get them off the bus at 4:10 p.m. Therefore my numbers are still ok. Does that make sense?