Ontario Highway Traffic Act

Hello, I have a 2005 Toyota Corolla - a 4-seater. I am going on a trip with 3 children. Two will be in the back seat. There is no room for a 3rd. Both children are 6 years old.

In the front would be a 9 year old.

If there is no room in the back seat for a 3rd child, are they allowed to sit in the front seat? We are heading out this Friday ...