Add functionalities to website reservation system

My website sells tours. The user selects from a calendar the tour date and number of people he wants to book for (check the attached file 1 to see how this works). Your job is to create functionalities in backend to set which dates are available for reservation and what's the maximum number of people that can be accepted. We need a way of doing this quickly for many days, but also for a single day. Check attached file 2 to see possible layout for doing this from backend. For example, we may need to set all Mondays, Wednesdays and Fridays between 2017-03-01 and 2017-09-30 as available dates in calendar. We may also need to later change availability for a single of those dates. After we set this in backend, the calendar in frontend will show which dates are available. When a user tries to book for an available date, the system will check how many people are already booked for same date (this is easy because all reservations are already being recorded in database) to determine if it can accept the new booking. The website was coded in Codeigniter and has a custom backend system that allows introduction of products into database/frontend and records reservations made at frontend.