Can I use only "buy now" buttons?

Considering that you have just 15 products to maintain, this shouldn’t be a hard task for you. First you must populate your store database with your products. After you have done this they will be displayed in the usual cs-cart front-end. Just copy from the html the appropriate form button for each of the corresponding products. and paste into your existing site. This should add the product to the basket page as you require.