Found this 2009 blog post doubting the authenticity of similar sketches offered by "The Autograph Store" (all links to same are now dead).
http://www.dograt.com/2009/05/26/genuine-faux/#comments
Makes the company in the OP look dubious at best. This kind of thing really bugs me, not only is the company scamming charities, but the end buyer gets burned too.