Custom eCommerce plugin for WordPress

Our client requires an online booking application for parties and events. There will be multiple party types each with a variety of additional options and addons which along with quantities will calculate the total for the booking in real-time. For ease of use we require a date picker or calendar function for the customer to choose their preferred day. There is to be a summary “docket” of the order on the right hand side during the process. e.g. [login to view URL] (This is a very similar process and layout to what we require). Payments are then to be processed via the Westpac Payment Gateway API (details will be provided for this). In the future we would also like to make use of Gift Vouchers in a similar fashion. This is preferably to be processed through the same eCommerce application however will be located in a different section of the website. Therefore there will be future ongoing work if we are happy with the outcome. It is important that the plugin is not only easy to use for the customer but our client needs to be able to update and add new parties as well as addons, change prices and descriptions within the admin area. A clean, user friendly interface is required. This needs to be in the form of a Wordpress plugin to attach to their current website and needs to be designed in the structure of the attached JPEG. We don’t mind if you use an existing plugin and modify it to our needs or construct one from scratch. (please advise which route you will use when bidding) Our client is very fussy and therefore may require multiple revisions and possible changes please include this in your time and quote. Please PM questions if you are unsure about anything. We have already had our time wasted by one freelancer.