It is not the accommodation that is ideal at this point, since he is coping most of the time, but now I really am in a corner of being branded as a prima donna mom who has to have it her way or accepting what they're offering.
I don't think it's quite this black-or-white. My suggestion would be to accept the offer (in an email reply), but also call an IEP team meeting to discuss how to move toward a solution that would promote your ds' independence. While it's a wise idea (politically speaking) to accept this solution for now, you don't have to accept it as a long-term solution at all. Using an electronic device as a planner for writing down homework assignments is a common accommodation, and moving students toward independence is a win-win goal for staff and student. I'd propose to the team that the assistant help phase-in the electronic device, and once he is functional and using it independently, they can phase out the assistant.
I would also make sure that if they are offering an assistant, it's written into your ds' IEP accommodations.
And bummer about the situation with the science teacher. FWIW, we've really noticed an increase in ability to self-manage for our ds12 during the past year too. I'd often heard that EF challenges sometimes improve with maturing through puberty and I think we've definitely seen that with our ds.
Good luck with your school -
polarbear