First of all, do what you think your family would enjoy! Since you're planning on going to a lot of non-Disney parks, your boys probably won't care too much that you're not going to the Disney parks also. All depends on their preferences, I guess.
Camping at Disney might be a tad more expensive than elsewhere but it is still a very low price for accommodation and comes with a spoonful of pixie dust
so I totally understand why you want to camp on Disney property!
I'm sure you'll love your vacation!