Happy Birthday Al.
I was faced with the same thing three years ago with my mom. I set up a camcorder in the living room, and over the course of the last few weeks that she was strong enough, we just talked. I got her to tell me about her life, from when she was a little kid, all the say up to the present. I asked her about people and family members that I didn't know very well, or couldn't remember much about, and about specific events in our lives. Much of the time, we just talked, about anything and everything. We had a lot of good hours reliving the years, and as we talked, in depth, she provided a lot of information that I had never known before. I got the kids involved whenever I could, and they would sit on her lap, or beside her, as she told the family stories.
Now that she is gone, the tapes are priceless. When I or the kids really get to missing her, I just pull them out and we watch them. It always makes us a little sad, at first, but after we're done, everyone has a smile on their face. I'll pass them down to the kids, so that they'll have something to remember her by, and to document the family history that she was a part of. Hopefully, I'll get to do the same thing with my grandkids. If you haven't done so already, you should think about doing the same, because your remaining time with your dad is also priceless. It will help in the years ahead, believe me, especially on those days, when you just miss his laugh, or his smile, or would like to hear him tell that one special story again in the way only he can tell it. My dad passed suddenly, quite a few years before my mom, so I never got the chance to do this with him, and I really regret that. Take care.