I did a similar road trip a couple of years ago in Germany and France, so I get the prep work! You're right that Canadians don't need a visa for the Schengen area, and 3 weeks is well within the limits. Your passport valid until 2029 works without any problem.
That said, one thing nobody mentioned: check your remaining validity carefully. I'm not saying you're close to the minimum, but technically some countries want your passport to be valid for at least 6 months after you leave, even if you're only entering for 3 weeks. In practice it usually goes through at customs, but why risk stressing yourself out at the border? With 2029 you're totally fine, so it's just to be safe.
The other important thing: when you enter Schengen, they'll scan your passport and calculate your 90 days. Keep track of your entry date, because after that you need to stay in the Schengen area for 90 days without counting your days of stay. You're good since you're only doing 3 weeks, but I've seen people get confused with their calculations and panic. Have a great trip in your van, I'm jealous of your adventure!