Start up agency booking problem

Hi,

Recently been working on a side project for my area. It serves a huge amount of tourists and there are many experience companies. Basically my website sells these experiences for them like a agency would. Ok so here is the issue with some bookings.

So if a customers books a (example) skydive. He orders off the website and receives booking confirmation with his confirmed time if needed (Not all need time slots, they can just turn up anytime to the event). What do you guys think would be the best way to sort out the booking times for those experiences that run off a specific time schedule. As if they book directly on say the skydive website they can pick a exact time.

I thought maybe a few ways i could offer:

- Offer a approximate time (Morning or afternoon) then they are given a number to call and book exact time? Could have problems if they get filled.
- Work with the experience company and integrate their booking timetable. (May be difficult and time consuming to try and integrate it.)

It needs to be as automated as possible so no human intervention except for say questions or complaints. Please give me your insight on what you think would be the easiest way to do this.

Thanks