Auto posting to Facebook page
Thanks everyone.

What I was able to do was build a Rule with Form Events that sets the 'Post to Facebook' checkbox (and one for Twitter) if the current page URL matches the node edit URL.  This way only the creation of a node, and not subsequent edits, are posted to FB...

I was initially going to do a hook_form_alter, but once the initial Rules test worked I figured I would go with it.

Rule Export >> 

{ "rules_form_alter_post_to_fb" : {
    "LABEL" : "Form Alter - Article Post to FB and Twitter",
    "PLUGIN" : "reaction rule",
    "OWNER" : "rules",
    "REQUIRES" : [ "rules", "rules_forms" ],
    "ON" : { "rules_forms_article_node_form_form_built" : [] },
    "IF" : [
      { "text_matches" : {
          "text" : [ "site:current-page:url" ],
          "match" : "http:\/\/www.example.com\/node\/add\/article"
        }
      }
    ],
    "DO" : [
      { "rules_forms_set_default" : {
          "form" : [ "form" ],
          "element" : "checkbox:fb_stream:fb_stream_do_post",
          "value" : 1
        }
      },
      { "rules_forms_set_default" : { "form" : [ "form" ], "element" : "checkbox:twitter:post", "value" : 1 } }
    ]
  }
}