I could not find anything from google so I will ask here: If I have a free night certificate from an Amex SPG Personal card a free night from an Amex SPG Business card, can I use them for a 2 night reservation and do I have to do anything special? Or just apply the 2 nights at the checkout page? Or do I have to book separately 1 night and then call/message Marriott to combine. I don't have the certificates yet so I cannot test it.

As an added wrinkle, how would this work if my significant other also holds a card that generates a free night certificate? Does she have to book? Can I add it to my reservation (since I am Platinum). Thanks