multiple google calendar accounts

We are in the process of updating our site and i love the Appointments+ plugin. My question is, we have 100+ calendar accounts that need there own appointment scheduler on their individual sub sites. The Main site is a Multisite and the plugin is network activated. Do i need to create a new api key in the google dev console for each individual calendar? Is there no way to sync the calendars through 1 dev console? We do use google apps for business for our company if that helps. Also purchased glogin plugin to facilitate the login process.
I found this plugin ( would it be helpful?

I know in the current setup the previous developers used 1 project in the api console, but that was all a custom coded theme.

Thank you