Polynatural, I do commend you on setting up your own poly website - nice looking format. And it is your website, so you can choose your own definition of polyamory for your site - although I don't necessarily understand the merit in constructing a definition that is different than the definitions of such well established and widely respected poly sites as morethantwo.com and polyweekly.com, not to mention the Oxford dictionary - all of which include some variation of "knowledge and consent".
The issue is - as Vinsanity pointed out - that without knowledge and consent, the "multiple simultaneous romantic relationships" could all be happening as dishonest affairs - plain and simple cheating - hardly what the dictionary and poly community considers to be polyamory.
But, again, you are free to define polyamory as you like on your web site - but some might see it as a disservice to the poly community to postulate that poly is no different than a married person having multiple secret affairs going on, while lying to their spouse about them. Just my two cents.
Al