Note that completing an Airtable form always creates a new record.
You could send a link to a form with all the existing information prefilled. The Prefilled Forms app makes generating the url for this form easier.
You would then need an automation to combine the data from the original record with the new record, and then delete the extraneous record. The exact solution would depend on whether you setup the form for the same table, or a newly linked table with the same fields. Deleting the extraneous record would also require a scripting automation, as there currently is no delete record action.
An alternative is to use a 3rd party portal, such as miniExtensions.
