Can both persons in an IBO membership opt in and update the Auto-Renewal Card?

No. If you have an IBO partnership with 2 names you must log in as the Primary applicant (has P next to their name) as only they can change renewal options and store cards for renewals. This was a business decision to prevent duplicate renewals and in no way reflects adversely on the secondary applicant. The Primary applicant is simply the IBO whose name was first listed when you were registered.