Do you think I should try to ask or better not risk it?
I can suggest from my experience which was similar to yours. A lot would depend when your flight is vs your ceremony date;
Don't postpone your ceremony yet.
I would suggest to attend the ceremony. Once you enter the Zoom call, after few moments they will tell you that you will be sent to a virtual room with an officer who will ask you to cut your PR card. But before asking to cut your PR, s/he will ask if you have any travel scheduled and if that's of any emergency matter e.g. sick parents/family death etc.
If there's no emergency, let them know that though there's no emergency, however, you'll lose thousands of dollars as you may not be able to travel - so if they can mail on priority.
If they agree to mail you next business day then you may be able to receive it within 3 business days.
You can ask they will suggest you to postpone your ceremony. They can’t just take a decision for you and eject you from the ceremony
I disagree - If the officer says that they can't guarantee when certificate will be mailed out - then it will be up to you if you're going to postpone your travel or postpone the ceremony.