There is a straightforward (if slightly limited) way to bring a guest into a Teams meeting. This Microsoft article explains how to join a meeting without a Teams account.

This process assumes that the guest does not have a Microsoft account. The guest will have to use Edge or Chrome as the browser, and their interaction with the meeting is limited. (LDT testing in November found that guests could not use their video/voice at all; testing on 12/8 indicated that only the whiteboard and chat functions were unavailable.)

You can add anyone to your MS Team as a guest if they aren't at UVA. They will have to then either a) create a Microsoft account, or b) complete account verification (sometimes multiple times) if they have an existing Microsoft account. The process seems to have some bugs, but eventually works after a couple of verifications. 

Refer to Microsoft's article on how to add guests to a team.

It's worth taking a minute to look at the definition of "guest access" to ensure it meets the expectations of the faculty: Guest access in Microsoft Teams.