There is a mild push to "emphasize people first", i.e. not someone who is mentally disabled, but a person with mental disabilities.
Although having worked with clients who were, the term I learned and used as optimal was "adults with cognitive and developmental disabilities".
:shrug; I'm not suggesting that's "more correct", mind.
There's a mild pref to put people first, e.g. "a person with cognitive or developmental disabilities", but I don't think yours is offensive, although it might get a comment.
Like when I first became a wheelchair user, I would say I was "chairbound" or "wheelchairbound" - but someone pointed out that some people won't help people in wheelchairs in emergencies because of a mistaken belief that anyone in a wheelchair can't be removed from it (many can stand and/or walk some short distance, others can't). So "chair user" is much better. Not to correct anyone, just because it can help in emergencies or whatever.