Do you want to create the conference and save it like a draft and invite the parents later ? Yes, you can absolutely do that. Create the conference and select ONLY yourself in the Recipients screen and send the invitation. The Conference is added to the class calendar and can only be viewed by you. Parents cannot see it.
When you are ready to open it for the class:
Doing this will send the conference invitations to the parents via email and the conference starts showing up in the Class Calendar for all the parents in the class and they can start signing up