You can also try the WestJet Flight Deck if you're willing to stand all game and to stay in the shade. That whole concourse is open to everyone I believe.
Stangstag made a good point. If the roof is open, you could be baking that day especially in the 500s. While the Canada Day game will be a loud atmosphere, the Dome will be crazy busy. Consider the lineups for concessions and washrooms. As well, during busy games I find more crazier fans who get drunk always sit up in the 500s.
Otherwise, my favourite seating area now at Jays games are Club 200 around third base. Smaller sections, comfy seats, better views over the net, in the shade and 200 Level Concourse isn't as crazy as the 100 level or 500 level concourse when games are close to being sold out.