Although you say it's unlikely they would apply for another card, it would probably be the best choice. If the were to apply for the Chase Sapphire Preferred, they would be able to move all the points there and still have the ability to transfer to travel partners. And even though the points are worth a little less if booking through the Chase travel portal, the difference would be more than offset from the additional 50,000 point signup bonus plus an extra 5,000 for adding an authorized user. Also, the CSP waves the annual fee for the first year.

Just my opinion