You might like to have a look at Zoom, which is excellent software which can be used to create a virtual classroom. Basic accounts are free (sounds like this will do for your requirements), and paid accounts are very reasonably priced.
There is a Moodle plugin for Zoom, which allows you to set up meetings, embed a "Join" button and more.
You can share your screens, share webcams and audio etc. It also records your meetings so you can review them later.
Highly recommend it.