I've seen a lot of posts on skipping the final leg of an itinerary when flying solo, but hadn't seen anything with multiple people flying on an itinerary where just one person needs to miss the final leg.

Situation: My family and I are flying LHR-JFK-IND booked using BA Avios. First leg is on BA, second leg is on AA. I recently found out I need to go to SFO the day we're flying back from LHR, so I was hoping to fly JFK-SFO once we arrive in JFK. Do you know if my family's reservation will get cancelled on the JFK-IND flight if I miss that flight?

I assume it's unlikely that they come take them off the plane, but at the same time I don't want to put them under that kind of risk. I looked at cancelling the award booking and rebooking myself separately, but there's no award availability showing anymore.

Thanks!