Hey Andy - what a brilliant dad you are, you only want the best for him. I know it's a terrible shock when first diagnosed, however the care available now is first class and there is alot of support out there to help you. When first diagnosed it can consume your lives with so much information and so many thoughts going through your mind - it will and it does get alot easier.
My personal advice would be to buy a teddy or toy that he can practice injecting on, so his diabetes buddy, it will help him to transfer his fears and anxieties from himself onto another object and until he becomes comfortable doing it himself. As Spiker has said kids pick up on our anxieties so if it becomes stressful for him it will make it harder for him to self treat, so lots of positivity, talk through the benefits on him taking his insulin and try to make him feel that he is taking care of himself by doing so, try not to feed the consequences of not taking it.
He should in time get a pump which will make life alot easier as he can get on with school/sport etc without having to inject or think about his diabetes so much, in the meantime ask away, there's alot of advice/support here to help