Custom Open-Source Website Developer

Looking for a strong, professional custom web developer who can help us design and develop a website for a client. The idea is proprietary, therefore information can only be shared with those who are eligible candidates for hire. The website is similar to the following, but in the interest of preserving the privacy of our client, the actual business concept cannot be divulged. OVERVIEW Website to provide two main sections. 1) Those who sign up to receive reminders for upcoming events and offer ideas on preparation ideas. We are also considering developing this into a custom iPhone app for this service. 2) The other section allows personalization and customization of event ideas EVENT REMINDER FUNCTION SIDE Create a custom reminder service which allows users to enter their details first and then the details of the event that they want to remember. We would need a client database but not a lot of personal details for the events that they are entering into the reminder service. Things like the event, the person's name (first name, nickname would work fine), their city or region. The member would be given options for how to receive the reminder notification (email, text, etc…) as well as be able to select multiple notifications leading up to the event. (i.e. 4 weeks away, 2 weeks away, 5 days away, event is tomorrow, etc.) SERVICE SIDE The meat and potatoes of the project. This is a site based on a membership/online shopping structure. Through a FREE membership signup, clients will be able to view and download free templates for ideas, etc. If a client decides they would like access to the whole database of ideas, there will be a monthly subscription fee for there upgraded membership. We see the layout of this side of the website to be very department store/online store like where you would be able to navigate through the templates via categories, type, search description, etc. Similar to a Walmart type layout with sections to comment of template items, rate items, show similar items, etc. TECHNICAL STUFF: REMINDER SERVICE APPLICATION: Allow for multiple notifications to email, text, etc… Notification email would have links to related item ideas within the FREE item template database. SERVICE WEBSITE: Open Source please. Built on Wordpress would be ideal but open to suggestions (Responsive theme layout a must for easy mobile browsing) Database driven to handle client/inventory management Ecommerce/Shopping Cart module Payment Gateway setup. (Needs to be flexible enough to handle automated monthly subscription payments and global transactions. Possible Paypal integration but open to suggestions based on price/budget) CMS a must. Would like the ability to be able to update products and manage client database internally. Security on this is crucial. Would like to hear your solutions for site security. Currently for most of our Wordpress clients we use the BPS Pro Security plugin. Would be in charge of migrating the website to the LIVE host upon completion of the project Provide design comps for layout of website before development