Canada

Try to find more scenic rest areas along the way if you can. Taking a 5 minute detour to hit a picnic area for lunch with a nice view and space to burn off some energy is nice on longer trips and will help make it feel more like an adventure.

The Royal Tyrell is a great stop, I remember going there when I was about that age to visit my great grandmother. The Alberta badlands in general are neat, worth stoping by some hoodoos or other similar formations if you get the chance.

As far as other stuff goes:

The Fraser River and Hell's Gate in particular is worth a stop, when you get to BC. (Also a good menory from that trip.)

And while (as an Ontarian) I fully understand the desire to drive though the province as fast as possible, there are lots of great scenic spots in the western half of the province, along Huron and Superior. (As you get into the Sudbury>Thunder Bay stretch, in particular.) There are also some beautiful spots more in my neck of the woods (Thunder Bay>Manitoba border stretch) but by and large those are further from the highway and more of a trek to visit. :P

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.

That museum is great, and Drumheller itself can be fun to stop at and look around. Make sure you grab food before the museum as it can take awhile (you can also pre-order tickets/slots which can help with the line).

If you're going up to Edmonton, there's plenty of stuff at West-Ed Mall. My kids loved the water-park+slides and the Lego store. There's also an amusement park with rides

I've done the drive from Calgary to Toronto a number of times, one place I try to stop at every time is Kakabeka Falls, just outside of Thunder Bay. It's a beautiful waterfall with nice facilities right off the highway and it tends not to be super busy. Conveniently placed right around where I usually am ready for a chance to walk around without needing to hike for 20 minutes to get to actually see the falls.

It's been a very long time since I was there, but there's also the Saskatchewan Science Centre in Regina. I remember enjoying it as a kid, but that was almost 25 years ago, so it may have declined. Science centre are usually a great place to visit though, so it's probably a safe bet

There's always fun stuff in Banff and Jasper. Maybe a stop on the glacier?

The Canadian War Museum in Ottawa is impressive and would likely interest both you and your son

The Aquarium on Vancouver's Stanley Park is very kid-friendly and because it's inside Stanley Park it's two birds in one stone.

As someone who's spent most of their life in Toronto, I'm grateful to have learned a lot of really cool things in other parts of our country from reading this thread - thanks all ☺️

Reptile Gardens near Brandon, MB. Lots of cool creatures there, and only a 1-2 hour stop, so you don't have to take a whole day to do like a zoo.

I did the same distance, your time line is really tight, if you can extemd it I would. It took me 6 days travelling just at or below speed limit due to a trailer. First night i did campsite but I found setup and take down took so long that the rest of the stops I just slept in the van when tired rather than doing specific night stops. it will be lots of stops with a child. Some highway areas have nothing to stop at and so you will need to plan for these zones. Saskatchewan is boring as hell so hopefully you have car games etc for entertainment. Thunderbay has a Terry Fox historic site, which was a nice rest.

If you're taking the Trans Canada up over Algonquin park, there's the site of Canada's first nuclear reaction, there's a turnoff that overlooks the site with an informational plaque. I've stopped there a few times on the way to visit family and friends in North Bay.

Drinking myself to sleep every night.