The promotion is stating cash night required, the certs will count. While details are not known, lets say you want a 3 night stay can you pay for night one, use cert for night 2, then points for night 3 and then that will provide 6 credits under the promotion? - shorter way of asking would be asking if nights booked w/points would count for credit?

On a related note, can one book TWO different reservations under the same account for the same dates?
Book room #1 for 3 nights paying cash, one cert and points....then book room #2 for same nights paying cash, one cert and points?
(there is a reason for the question here, as booking a room for 6 nights using cash night 1, 2 certs and points (while an option) may not be advantageous as two separate bookings. If something went wrong where you need to contact support for credit, wouldn't want someone looking back at the reservations and saying what happened would not count... regardless if they were booked at the same hotel, or reservation #1 at hotel A, and reservation #2 at hotel B.