I wouldnt say either are reasons for your DC not to go there to do homework after school. It is supervised from about Feb half term till end of external exams. One of the computer rooms is usually open as well.
There are probably clubs on average 3 nights a week that a year 7 could go to- whether your DC is interested is another matter.Choir runs every Wednesday and has great tours as an added bonus
To be fair the school aren't going to want to take responsibility for after school care so my guess is they will be careful about what they say but depending how flexible your DS is and what your timings are you could probably put something together.
I guess an alternative is to look for a childminder he could walk to after school for an hour or so?
Do hope you get it sorted.