At our college our teachers regularly email us so this is a good idea.
There is always that saying, "blah blah blah ...at least you have your health" now I know that this is not your health, but it is someone's very close to you and it is important that you see them. Judging by your GCSE grades you're extremely capable, thus it should be too much of a problem - however ASs are not just about gaining grades, but more importantly UMS points. So this is a tough one.
Personally, I'd go and then just work my socks off when I got back. Taking some work is a good idea, but not too much as I think that I'd much prefer to have some time with my family to relax and concentrate on them, as opposed to stressing yourself out. Your AS exams will go so much better if you are calm as opposed to stressing out over them and this period could chill you out. Go for it!!!