Hi @EllenSpertus ,
The answer to your question depends on how your course is set up and rostered and whether you have to sync to a separate Student Information System (SIS). If you have the rights to create sections, you could create a section for these students and then assign things to that whole section for a different date. They could also remain in the main section (the whole course roster), if needed/desired; students can be in more than one section.
Some caveats:
Your institution may not allow you the rights to create sections.
If you need to sync to an SIS, creating more sections will interfere with that process. A workaround is to send grades manually.
If you use Canvas Attendance, there may be ramifications from adding sections. I don't know because I have never used that program.
Note that you cannot use Canvas Groups for the purpose you describe; the Groups feature serves a different purpose.