When following the instructions in the Canvas invitation email, or from the article: Create and Sign In to a Parent or Learning Facilitator Account in Canvas, some scholars report that the option to "Pair with an Observer" is not available.
The Pair with Observer feature is only available once a scholar is in at least one active course. If you are trying to complete this process before course enrollment imports complete, you may find the setting is missing.
We are so glad you are working on this, and look forward to seeing you in Canvas! Please try again on the first day of school.