Congrats on your son's accomplishments.
When my youngest son ("high functioning" autistic) was about 15 I gave him my old Diamondback "city bike". He was able to learn to balance very quickly. He rode all over the neighborhood but even though it had a 7 speed cassette, he never shifted gears. The chain stayed on the middle chainring and the middle cog.
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The Lord is merciful and gracious, slow to anger and abounding in steadfast love. - Psalm 103:8
I am a cyclist. I am not the fastest or the fittest. But I will get to where I'm going with a smile on my face.