Sorry,

If you think about what I posted and if you envision this becoming a "BUSY" site and business....trying to manage many separate html pages, orders, payment methods, shipping methods, stock and all the other items that encompass an online business and that your current site does not address I think that you will find that using a stable application like Zen Cart (or another that you may choose) will benefit you many times over in the long run.

Have you considered how you are going to manage stock?
Sales?
Inventory?
email notifications?
payments?
etc?

Yes you can invest your time and effort in writing all of these into your site...

Or you can invest considerably less of your time into learning the basic requirements to add your elements to one of the packages available letting it handle all of these issues...and of course, here we are biased toward Zen Cart (and for good reason) as many of us, myself included, are only volunteer posters here and we could be on any site we choose.