Multiple spots available for same time period

There is some related info about this subject in the following tread.
So Now I need to do the same thing but add service providers to the mix. I can't seem to make it happen. I need clients to be able to book 2 clients at the same time but I want to offer this option to multiple locations in the same web site. I use my Service Providers as a physical location. Also, I would like to have the ability to have a few of the locations to be able to book 3 therapist at the same time.
Can this happen with the functions.php code?
Should I try to make this happen another way? Like using membership plugin?
I have granted access and I am using page