Long division is pretty much obsolete except you do need to know how to do it well for algebra when you divide polynomials. Tell him that. There is something about long division that is different from other math - it's very procedural and it's about lining things up and writing things out a certain way. My non-mathy DD actually pick it up more easily than my somewhat mathy DS although she was 8 and he was 7 due to his acceleration. By picking it up, I don't mean getting the right answer, but being able to write everything correctly step by step all lined up.
I am not certain what level of calculation your ds is able to do mentally - I have encountered some savants who could do calculations like a computer. However, if you are only talking about double digit divisors, then simply add a decimal and a place value or two so that he will need to write it out.
