That is a very honorable thing you are doing for you friend's Widow and daughter. I'm sure your friend would be pleased that you are helping him, ever after he has passed - and he would also be pleased that someone like yourself is working on his games.
I work at my own pace as well - I maintain the "fun factor". If it becomes stressful or laborious, I find something else to do. Sometimes I work all day and then only an hour the next. It is all about finding the time and looking after the more important things in life.