Ambleside Online's Composer for the 2011/12 school year's second term is Felix Mendelssohn.
Portrait of Mendelssohn by James Warren Childe
From AO's composer schedule, here are the selections, including his Octet, which, according to Wikipedia, was composed when he was only sixteen years old:
2011-2012 TERM 2 (This term's artist is Albert Bierstadt, landscape) Felix Mendelssohn (1840) (Romantic)
Listening selections for this term:
Songs without words (there are 8 volumes, 8 different opus numbers. notes)
Violin Concerto in E minor, Op. 64
Symphony no. 4 in A major, Op. 90 ("Italian") (4 weeks)
Octet in E-flat major, Op. 20
Fingal's Cave ("Hebrides") Overture, Op. 26
Here is a Grooveshark playlist of the above selections in the same order you can play off of your computer.
View of Lucerne - Watercolor by Mendelssohn, 1847
I also found a download on Project Gutenberg titled "The Great German Composers" by George T. Ferris, which contains a biography of Mendelssohn as well as others. I also found it available at no charge for the Kindle on Amazon.
It seems to have short enough biographies for me to read and tell something about the composer to the kids, but I haven't read it through to be able to comment on it otherwise. If you know about this book, please add a comment to this post and share your thoughts.