I wonder how many precious stories are lost because people don't have the skills to put pen to paper. Maybe some people think their narrative would be of little interest to others. Maybe the embarrassment of not picking up the basics of grammar, spelling, or punctuation in school is preventing them.
Sad, I think. I'd relish reading about a family member's actual thoughts, hopes, desires or events (or listen to them) in ANY form than have them vanish for all time.
Unlike teachers grading "What I did This Summer," I don't believe our descendants would sit in judgment over silly communication errors. There are volumes of reasons some school lessons don't stick. So, please. Don't worry about rambling, about fragmented sentences, about improper use of pronouns, or even about spelling.
A journal is a safe place to record your reflections.
Spurred on by a conversation with an old friend, your autobiography can be completed in an afternoon.
Consider other forms for sharing your stories--like gathering the family's favorite recipes or compiling a scrapbook or album.
I think they would be delighted to learn more about you.
At least I would.