RE: Help me be a good uncle
Leave him.
Give him a brief explaination. When you get back you can give him a more detailed explaination going beyondhunting. How he shouldn't have to be told 3 times to do things. How priorites should be lined up. How what needs to be done always comes before what you want to do ("needs" before "wants").
Maybe just forget about hunting with him for awhile until he initiates it. See where it lies in his mind.
Let him know you were counting on him. How you wanted him to be there. How you were looking forward to it, etc.
And at 13 maybe a little talk about some other wild game? Birds & the bees?
But above all - let him know regardless that you still love him and that's the reason behind leaving him and the talk. Start the talk with "Because I love ya and care about ya......" and end it with the same.