I would use the "excuse" if you have to explain, about your father's death and having to take time to straighten out your mother and his affairs, etc. People will respond "kinder" to that I think than to your own problems?

It's awkward at first going back to work after an illness, even just a physical one. I had some of that in 2003. Someone else has been doing your work (sort of) and the company has been continuing on and you have to fit back in. Too, other people (despite your uptight "boss") will genuinely care how you are and will have heard different rumors/stories as to why you were out, etc. so maybe make up a couple versions, short-and-sweet for those just asking out of politeness and another, slightly more "personal" one for those you think care. But I wouldn't bring up anything on your own, unless you have some good friends among your coworkers and even then I'd wait until you were away from the office to fill them in on what has been happening. Think of it like, "Hello, how are you?" which is both a run-of-the-mill greeting to which everyone always answers, "Fine! How are you? Lovely Fall weather we're having, isn't it?" :-) as well as a serious question where you say something like, "Not too bad; you know my Dad died?" and then add another sentence or two for those you think truly care, depending on their response to the "you know my Dad died" question.