A subdomain will work just fine.
However, just FYI, on most servers, subdomains are just like an alias that points at a subdirectory on your server.
http://subdomain.yourdomain.com
really just points to;
http://yourdomain.com/subdomain
If the products you are selling are what the rest of your site is about, then I would think that you would not want a separate domain name for the blog. I would simply install it on the server, either in a subdomain or just simply in a directory of it's own witout a subdomain.
robert