I think a lot of it depends on how you feel, and to a smaller extent, others too.
When my father died I took a week off, but there again my parents were the other side of the country and I felt I needed to help my mother get through all the official stuff that needed doing. I recall when I returned my boss said that some have commented on me taking that long, but I retorted that if they wanted to say anything they could come speak to me and I'd tell them what I thought. No one did. Point is you only ever have 2 parents, so if on 2 occasions in your life you take time away to do what needs to be done, then that is your decision. The rest of the world, including your employer, can go hang. Obviously don't take the Mickey though. None of us have any preparation for this sort of thing, we have to play it by ear when it happens.
As for the wedding, see how you feel. On the one hand it is good to carry on the normal things of life; gives a break from thinking about the recent tragedy since you are out concentrating on the occasion, and keeping a stiff upper lip. and of course having the support of friends around you while you are there. But don't feel you have to go, or if you do, don't feel you have to stay for more than is polite if you'd rather leave. I'm sure the wedding couple will understand.