I learned to sew when I was 8 years old - it was an electric machine though. And I have always been tall for my age. Seeing your machine makes we want to go back to my aunt's in Kansas and see what the treadle Singer looks like in the cabinet. (I know it was used A LOT because my great grandmother was a professional seamstress.) Also, would give an oil bath just because I know one has used it in over 40 years. My grandmother didn't sew, and my mother used her electric 15-91 after 1950 and my aunt that has the machine never sewed. My grandmother said there was "an old man" across the street that used to borrow it from time to time to sew leather. Oh sigh! Sure wish my daughters liked to sew. You are very fortunate your nieces are interested.