How many of these options does he get to choose? When I took my GCSEs I had 4 free options, so if he only gets two that seems quite restrictive. Regardless, I will try to help as best I can.
I took Drama at GCSE and whilst I didn't do as well as I had hoped (I got a B), it was a very enjoyable subject. Exact content will depend on the exam board but if he is considering Drama ensure that he knows it is more than just practical work- he will be required to write essays and if this isn't for him he may want to reconsider. Although it wasn't all fun and games all of the time, Drama was a nice break from my other subjects which had higher workloads and much greater pressure to succeed. However, enjoyment of the subject will also depend on your teacher, so whilst it shouldn't be the deciding factor if he likes his Drama teacher that might be something to consider as an advantage to taking the subject.
Several of my friends took Music, and again it is a lot more challenging than you might expect. You need really to be able to play an instrument to grade 4 or 5 standard if you want to be succesful, so if he doesn't meet this requirement it isn't really an option. Again, enjoyment depends on the exam board. At my own school, I decided against Music because I didn't feel passionate about the content and felt that my grade might suffer as a consequence. There is often a composition aspect, which I know a lot of my friends found quite stressful, although GCSEs have changed a lot over the last couple of years so the way that this is done may have changed, so this is something to be considered.
At my school neither Psychology nor Media Studies were offered at GCSE, but I would say that these are two subjects that you can generally take at A-level without prior experience, and so if he is not sure that he is interested then perhaps they aren't the best option. In addition, if he by any chance suffers at all from mental illness (anxiety, depression, etc) I would highlight the fact that in the study of Psychology there is often a view of 'otherness' placed on the mental illnesses discussed, especially at this level, which some people find upsetting or just annoying. In terms of Media Studies, I can't really contribute much beyond the fact that it isn't always the most respected of subjects. For these, I would recommend researching the content by finding the specification for your schools exam board online.