Sorry to hear about your situation, but you must be certain that death is an inevitable part of life. It is certainly sad that some people may go away earlier than expected, and we have this notion that a person may somewhat "live a while longer" as we keep their memories alive with us. After a loved one dies, mourning certainly is an important period to help us get over this fact.
No matter how many pictures, videos or journals you make of a person while he/she is alive, nothing will replace the fact that this person is really gone. Fading memories are part of an essential process where we leave them behind and move on with our lives. We will certainly remember and honor our loved ones at their best and most marking moments. But holding on to so many specific details about their lives takes an incredible unnatural effort. The longer we try, the more difficult it becomes to remember specific details. And this is natural! The more we strongly hold on to a person after he/she is gone, the more difficult it will become to keep living.
Please, don't understand me wrong. Unfortunately, that's how life goes on. It's hard, but inevitable.
I hope you make the best or your time together. And my suggestion is "stop trying to record every detail of her life and spent more time with her as a family". Your own memories of this time together should be well enough to help you get over the hard period when she's gone. In the future, when you look back, anything else will just make you seem like "the guy behind the camera".