Teaching in class and online cohorts CS
I am in an almost identical situation to you, and I suspect that many, many CS teachers around the world are in similar boats right now.
I think you're right about the fundamental truth of it; you cannot keep different students coordinated if they do different things, and you cannot have them do the same thing unless the online-only cohort can also participate.  This leaves us with the sole (unappealing) option to treat everything like distance learning.
That doesn't mean that there are no advantages to the new arrangement!

The kids who will be with you in person will be able to easily and directly ask you questions.
The kids in front of you will also be easier for you to informally poll if you want to check in and make sure that what you're saying isn't losing the majority of the people.  (When I say informally poll I also mean to just scan your eyes around the room, and use your teacher-instinct to see whether many kids seem lost.  This was very hard to do during purely online education.)
Some kids were getting lost during purely virtual instruction, and having them in person some of the time will give you a chance to talk to them face to face, and hopefully to reel those students back in.  I suspect that coming in to school at least some of the time will make the entire thing seem more real, both for you and for the students.

If your in-class kids each have an electronic device, you should make sure that they have headphones to avoid audio feedback issues.  If they don't all have devices at school, you may need to do some photocopying, or &quot;play&quot; your materials at them from the front of the room.
Here's to hoping that this whole mess is very temporary.