Class 3
KENDOR RECITAL SOLOS is fantastic. Its a book of class 3's that your kids will enjoy. You can also get the same book for almost every other instrument.
also:
Kendor First Solo Album For Horn
Allerseelen - Strauss/Voxman
Autumn Dream - Lotzenheiser


Class 2
Etchings - Schudel
Romance - Saint-Saens
Andromeda - Beethoven/Poole

These are all on the easier end of their respective lists. Of course all of the Dishinger arrangements are library staples, but personally my kids think they are a little "boring."