Are you going through Toronto or taking the 417 around it? If you're going through TO, hit the Science Centre. It may be your last chance to see it before Ford destroys it - he wants to tear it down and build a smaller version on the waterfront. And there's also the Big Apple which is a fun little pie-shop with a giant apple-painted water-tower in Colbourne. But that route would only make sense if you're going through the USA until like Manitoba or Saskatchewan (in that case: Milennium Park in Chicago, London Children's Museum in Fake London, and Pinery Provincial Park for the best freshwater beach in Canada).

If you're taking the 417 and going North through Ontario, I strongly recommend Science North in Sudbury, which is an amazing science museum your kid will love. There's also the Big Nickel there which is a nickel mine converted into a museum of mining, if you've ever wanted to go down into a mine.

For camping near Sudbury, I recommend Killarney Provincial Park. It's an amazing landscape like nowhere else I've ever been, since it's so rocky - all the foliage like pine trees and wild blueberry bushes are growing out of cracks in rock. Nothing like sliding down giant rocks into the water for a swim. In the Ottawa Valley, Bon Echo park is similarly beautiful rocky landscape. Both these sites were the subject of various paintings by the Group of Seven. Bon Echo is an excellent "my first time in a canoe" camping trip because there's a very short canoe-across-the-lake then hike up to the top of Bon Echo Rock for a nice little bite-sized adventure to an amazing view. But both of these provincial parks may already be fully booked up.

Most of these are afternoon activities, not little "20 minute stops". Honestly, I'd think hard about changing your plans to buy yourself more time if it's at all possible. I mean, when are you ever going to be back in Sudbury if you're moving to Vancouver? You might see Toronto again one day, or Montreal, or Ottawa. But you ain't ever going back to Sudbury, and it's worth a day or two.