When you say that "Add to XYZ Area" doesn't show up in the canvas, do you mean that you have a canvas element around the entire page, or around the area php code in your page template? My understanding is that's not how the canvas element works -- you can't just have arbitrary html elements inside of it, but rather need to draw everything in it with javascript. If you want to use canvas, I think you'll need to make it so just one block outputs the canvas element from its view.php template.

The canvas element I'm talking about would just be an area on the page. I'm thinking that I'll be taking the block approach, though, since that seems to make more sense in this case anyway. So, looks like I'll be working on a block that will be included with theme! And... who knows.. I may even release it as a stand-alone block!