Yes, it should be no problem at all. You can also reserve the room through internet, add the names of the guest; use your Marriott reward points. I think the online reservation portion of Marriot.com website works like charm; other parts at times are very slow, local maps are questionable.
I agree with the other answers. Easy to do. I've done it quite a few times. One caution. If the person staying is young enough (teen or young adult), make sure they have a credit card. If they don't then you have to go through a paper process with fax from the particular hotel for your credit card to cover them. They fax a form, you complete it, you fax it back.