Lene, I can't off the top of my head think of any, but my first suggestion is to ask for recommendations of well-written family-focussed (auto?)biographies. The first that came to mind was Dawn French's
Dear Fatty, though I must admit I haven't read it - I just like Dawn French.
However, hopefully some will be along with some suggestions.
In my subjective opinion, I wouldn't write it to or for children. This does not preclude it being read to or by children, but if you give yourself that specific limitation I suspect you may suppress being forthright, and limit your scope. Write to an adult in a clear, concise, simple, open and friendly manner, and I think you'll find that the side-effect is that child-friendliness will come built-in. Even the slightly salacious moment, or the occasional "blue" words, remembered and written (if not extending into gratuitous or extreme) can be read by children, and often with some more delight than even the adults get from it.
I personally wouldn't call it anything yet. If you want to give it a working title, something simple like
Family Secrets or
Family Traditions will work, but I think you'll find the title will grow in your mind out of the content you write. Don't let a title get in the way of starting though.
Ideas? I don't know. Perhaps you could write it as a calendar of significant dates. So, for instance, you might have a chapter called "December 25" and write about memories and Christmas traditions (and recipes, yum!). You might have a chapter called "March 27th", and write about how you first met your partner (assuming it was on March 27th, which it probably wasn't because I just pulled that date out of the air, but you get the point.
). Build it as a progressing calendar year of significant dates (almost like a year-long advent calendar?), and it doesn't matter if the content of the chapter stretches well beyond that date - the point is that the date marks a moment around which things occurred, before and after and even into the future.
That's just an idea though, and probably a stupid one. There's always Dawn French's idea of writing letters to people.
Cheers,
Marc