Hi Larry, we have created Zoom and Teams as rooms as well and include the login information in the details of the seminar activity.
We have been doing what you are suggesting in changing the 'room' to trigger a change notification with the login details to the attendees. Not aware of any other way to do it (other than sending an attendee message but that won't update their calendar info).
I would be interested to know if there is another workaround.
Regards
Sue