You should take him anyways.
You are introducing a negative stimuli, which does not necessarily cause him to reflect on his actions. In a few years when he will be legal adult, he will be able to go to a DT show even if he behaves poorly. What you want to do rarely succeeds in conditioning behavior because he does not understand WHY what he did was wrong and the reasoning as to why he should not do it again. If you do not take him, he is likely to just get angry and as he gets older, he will rebel. It's a common mistake to use negative reinforcement to educate kids. It is much better to try to explain the reasoning in the hopes of getting them to consciously choose not to repeat the behavior. That's the most effective form of discipline because generally, if the child reasons and concludes that they should not bring an iPod to school for a valid logical reason, then they are highly unlikely to do it again. Otherwise they will just feel that they are treated unfairly and will aspire to rebel and live moments of youth when they get older.
So if I tell my son to clean his room and he can have cake after dinner and he refuses to clean his room he should get cake. Because he won't understand what he did wrong? Wouldn't giving him cake, or taking him to the DT concert show him that it's ok to break the rules, because you can get away with it?
I would not make those reward-able outcomes to begin with. It boils down to the same sort of conditioning. As an adult, when he will clean his room, he will expect a reward to be given that is completely unrelated to the satisfaction of having a clean room.
The issue with reward-able outcomes is that they are rewarding good behavior with something unrelated.
What can happen is:
Well, I cleaned my room, but no one prepared a destert for me, so I will stop cleaning it in the future.
Rather than:
As dad/mom explained to me, keeping a clean room can:
-Prevent me from tripping on my stuff and hurting myself
-Help me find my stuff faster and therefore waste less time looking for my stuff
-Give me good practice for staying organized now for when I will have no choice but to be organized when I have a job
-Make my room less dusty and prevent me from sneezing from allergies or get sick
-Make me look responsible when I have friends or company over
These are all advantages that should be understandable by a certain age group. There are also very compelling and logical reasons as to why mom and dad should not clean your room for you too.
At least for me, this sort of logical conditioning was very effective for me growing up. I get a serge of dopamine from seeing a clean room as an adult because I associate that with all of the aforementioned positive outcomes directly linked with cleaning my room.
In the same regard, the DT show should not be viewed as a reward-able outcome of behavior (in my model). This will build expectancy that he should receive an unlinked reward as large as going to see a DT show just for not bringing an iPod to school. What will happen is, even if he stops bringing it to school this time, and went to go see DT, he would just start disobeying straight after because there is no longer any incentive not to do so.
This is because the real positive outcomes of obeying the rules have not been explained. The reward-able outcome is no different than if I told you: If you paint my roof, I will bring you to a DT show. That certainly will not lead you to repaint my roof the week after the show will it?
That's the point I am getting at.