First time poster... would appreciate some help please. Apologies if I have posted in the wrong place and happy to delete and move it if advised. No marriott status just a bonvoy member.

Took advantage of the buy points at 30% off promo. Booked two rooms for 5 nights in Oxford, UK for the summer. One room for myself and the other for a couple of friends.

(i) I've called Marriott to add one of the friends as the guest name to the second room. I understand the e-certificate issued name has to match. Is there anything else I should do?
(ii) We will arrive at the property 9pm-ish. What is the risk of rooms being given away to paying punters? I can probably get there for 3pm but my friends can't get there before 9. Is there anything I can do to mitigate that risk apart from emailing the hotel manager?

Would be grateful for any advice as am new to the programme.