Writing About a Relative: Tone is Difficult

I've started the wording accompanying the photo archive of the cars and have encountered some problems - namely what tone to use when writing about / for an elderly relative.

I have written and re written countless paragraphs trying to get the tone just right, with the results ranging from faintly mocking to obituary-like. 

It's actually a really interesting subject for me, how tone differs in context and how important the resulting choices are on the final piece.