To be perfectly honest, I would firmly tell my counselor/therapist/M.D. I am going to my son's performance. They can figure out how to make that work.
I'd only expect a problem from them if they could honestly say I am a danger to myself or others. If that is the case, I would expect IP instead of IOP.
It's really contingent upon how
you feel about attending vs. not attending.
If you are well enough to attend, I'm sure you'd like to do so and will likely feel badly about yourself if you don't attend.
If you are not well enough, you'll need to find acceptance.
I think it should be
your call.
Just my humble opinion.

WC