What kind of infrastructure for using IVR

I would be using FreePbx’s IVR functionality for clocking volunteer tasks and nothing more. How much pressure can such a system take if my volunteers are clocking in around the same time? They don’t all start at the same time but I will expect heavier traffic in morning and at night. There will be roughly 100 of them. They will all be local to a region and I want a local number. What is your recommended setup for my situation? Do I need a dedicated server, appliance, remote server, phone line, etc.

Let me know if more info is needed.

It depends on how many simultaneous calls!
Look this page: https://www.freepbx.org/store/freepbx-appliances/