Yes, you can. After you make a reservation online at priorityclub.com for a room with 2 adults, click "current reservations" on the left and click "view reservation", then click the "edit" button on "Additional Guests (Optional)" part. Add your friend's name to the reservation. Your friend is good to go.

When your friend check in the hotel, ask your friend to tell (lie to... well, it doesn't hurt) front desk that you will arrive later with different flight. Since the front desk staff might think that you would arrive later, they would most likely give your friend an upgraded room because they can see your RA status in the reservation from their computer. I am sure front desk staff will not keep tracking/checking whether you will actually arrive the hotel or not. Even during check out, in case if they ask, just ask your friend to tell them you have already left the hotel earlier for the earlier flight.

I don't understand what you meant by "What is the best way of me booking it for the points? ", so I cannot answer this part.

Let me know if the strategy works after your friend get back from dubai.