We need additional functions on Wordpress theme

We really like this Wordpress theme and will purchase it [login to view URL] But we’d need to improve few things and just wondering who could help us and how much it could cost? 1. We need to have possibility to assign each coupon to specific date. It means that coupon is valid only for one specific date – buying a coupon you buy a service on particular date (for example, you buy a discounted coupon for meeting room rent on April 15th 2016, so it means you can use this coupon only on April 15th). 2. We need additional search field by coupon validity date. For example, I’m looking to rent a business meeting room on particular date, so I enter in the search field 2016 April 15th, and I show only those coupons which offer the service on this date. 3. Coupons which are assigned to specific dates should be excluded from search results once they are sold . For instance if the coupon is for business meeting room on particular date. If it is sold, it means that similar coupons can be sold only on other dates. 4. Possibility to create multiple admins with limited permissions to create and edit only their coupons. Each vendor which wants to sell his products or services via the website, will be allowed to login to the admin and create his coupons, set up prices and validity dates. But vendors should be limited to edit only their own coupons. The website will be in one languange. Please have in mind, that I'm not IT guy, so I leve the technical part of decission to you (maybe you will adjust theme, maybe ad some plugin or what ever...). If any of those functions are not clear, please contact me.