You've asked an interesting question. I've seen several Bar Mitzvah affairs done on Shabbat for cerebral palsy kids and those with all kinds of disabilities.
I have a close friend who has an autistic son. (IMO, I pray that no one should ever have to deal with this disability. In some ways, it's worse than dealing with a child with cancer.) He is somewhat verbal, but, he understands little of what's happening.
As I understand from my friend, on Shabbat, they had him come up to the bimah while someone else got the aliyah, and he kissed the Torah (with some help / prompting.) At the end of shul, he sang a song (for an autistic kid, BTW, he has almost perfect pitch and an angelic voice. You never know what talents hide, there!)
This is besides a full Bar Mitzvah "feast" that they made the next day with speeches, singing, dancing and the works. It was a true simcha.
What I mentioned for autism I've seen similarly done with cerebral palsy, cripples, blind and my son who is deaf. (Halachic issues involving cheresh may apply to Torah reading, etc.) The point is that, indeed, these are quite frequent among Orthodox shuls, at least in my neighborhood.
Deaf and hard-of-hearing people, fortunately, face fewer shul inclusion challenges today than about 15 years ago. There seems to be a general halachic consensus that profoundly deaf people may read from the Torah. (Definition of cheresh in the Gemarah is disputed, but has generally been interpreted as "deaf-mute" and the thinking, then, was that they were non-intelligent.) Today, many deaf people wear cochlear implants, and there's a general halachic agreement that an implant produces immediate sound equivalent to regular hearing.
You may want to view this article published by Our Way, a division of OU. As my son has been deaf for many years, we have been members of this wonderful group. For his Bar Mitzvah, we had him read maftir and the haftarah on Shabbat. As his Bar Mitzvah occurred during Chanukah (well, we postponed the celebration a few weeks to coincide with Chanukah, actually,) on Sunday morning, he read the double Rosh Hodesh / Chanukah Torah portion. If I recall correctly, a JSL ("Jewish" sign language. It's mainly ASL, but they translate Hebrew, davening an religious terminology; quite fascinating!) interpreter volunteered to interpret the prayers and reading for the few other deaf that attended on Sunday.
The practical halachot of cheresh today are somewhat complex. But, point is that not only are Orthodox Bar Mitzvah's done by deaf kids, but, they really try hard to include the hearing by publishing a Bar Mitzvah symbol booklet. If you've never been at a mainly "deaf" prayer service, as a hearing person, I can tell you that YOU would need a "reverse" ASL interpreter.
This article cites the numerous Orthodox shuls throughout the U.S. that accommodate various disabilities in various ways. The beginning of the article says:
A recent bat mitzvah program at Young Israel of Toco Hills, in
Atlanta, included an ASL interpreter. (Adam Starr) This story is
sponsored by the Orthodox Union.
Erik Bittner can pinpoint the exact moment he felt his son with autism
was truly included at his family’s Orthodox synagogue, Shaarei
Tefillah in Newton, Massachusetts. It was a Shabbat morning and the
gabbai – the sexton orchestrating services — called Bittner’s
24-year-old son, Nathan, up for an aliyah, to recite the blessings
over the Torah.
“Nathan whizzed through the brachot and he was effusive in his
gratitude for going up there,” Bittner recalled, using the Hebrew word
for blessings. “He shook everyone’s hand. It was a touching emotional
But the next week when Nathan showed up late and afterward asked why
he didn’t get an aliyah, the gabbai responded: “I only give aliyahs to
people who show up on time.”
Bittner wasn’t upset; on the contrary. He was pleased his son was
treated like anybody else.
“Real inclusion means those with special needs are held to the same
standards as everyone else — as long as those standards do not exclude
them,” Bittner said.