I recommend using silverlight when you have business logic that can be reused between the client and the server and you have control of the end users installation. Since you are talking mom and pop I would either try to use plain old HTML + js, skipping the canvas and html5 stuff if possible or going to Flash and actionscript.
The main reason would be the installation experience. The less savvy don't want or often even know how to install a new plugin.
I am concerned that Flash is like Silverlight in being a black box inside the browser and some platforms (i.e. Apple) do not allow it to run on their phones. In the long run I might want a mobile version of the site.
The main reason would be the installation experience. The less savvy don't want or often even know how to install a new plugin.