It is MUCH easier to take someone out of Commencement, even at the last minute, than to put someone in, which requires significant lead time. If there is even the slightest chance that you might be able to walk, leave yourself listed as attending until you are certain you are not going to attend. A False Positive is much better than a False Negative. If you are listed as participating in Commencement and you do not arrive at the ceremony, that is easily addressed. But if you are listed as NOT participating and you show up, that is a hard situation to rectify.