Are you try to creating a booking system in WordPress? Is this?
The approach you are following will consume too much time. Try using “Custom Types” plugins, there are plenty of good plugins in this category, and the normal way they operate is that they deal with the new added fields as custom fields, stored in postmeta and bound to posts, to utilize all post action filters and handlers. Your attempt means that you will recreate all of these filters and handlers that by the end should be bound to wordpress triggers and events.
Watch the following video tutorial for one of the available custom types plugins, to understand the concept, once you have it, try search the available plugins to choose the one that fully suits your needs:
Custom Content Type Tutorial