Thank you all for the great advice!
How did I finally do it? Well the sitting down and trying to explain, prepare, let him cut things did not work. At all. I found a you tube video about cutting kids hair, that did not work either. What did work was to sporadically during the day when he least expected it walk by him and super fast cut a piece. One cut at a time. I got a big part of his hair on the back of his head away while holding him upside down and tickling him. The rest was done while he was asleep. He woke up after a few snips so I had to space it out over three nights. Results? Let’s call the uneven bangs charismatic?