My aunt did this. Right after a divorce, she got breast cancer that spread to the lymph nodes, and game over. She had 3 small kids, and left them a video, which I was allowed to see as well.
I found it really sad. I'm sure she thought she was doing the responsible thing as a loving parent, and didn't have any idea anything else was seeping through. However, she clearly was still angry about the situation, and blamed her ex for the cancer. In the video.
However true or unfair that is, this was the decidedly not the person she was. She was a stunning woman, on the inside and out. She was the smartest person in a family full of postgrad professionals, and attractive enough to spend some time dealing cards in Vegas, and do stints on game shows in Hollywood. She did some really amazing things, and spent her life as the rockstar of our family. I can't express how sad it is to me that the last thing she left her kids with was none of that. It is just now how she deserved to be remembered.
I remember she specifically instructed her daughter about graduating from college (part of the inheritance was even tied to that) and choosing a partner better than she did. He daughter ended up dropping out of college to marry an older man, and has since divorced and remarried. I guess the moral here is that no matter what you do, your kids are going to grow up and make their own mistakes.
Please, please if you want to do this, watch it yourself and pay attention to what you are saying.