This is what I think is the difference between modern and contemporary dance. I hope it helps.
Modern dance is a form of dance developed in the early 20th century, in includes dance styles such as Tap, Jazz, Lyrical, ballet. Contemporary dance is a collection of systems and methods developed from Modern and Postmodern dance. Looking at dancers such as martha Graham, who was the first lady of contemporary dance.
Maybe you could suggest they watch some contemporary dance pieces.
Some good examples are
Swansong by Christopher Bruce.
Swan Lake Mathew Bourne.
These are good pieces that I am sure your girls would enjoy. Anything by these two cheoreographers will give them an insight.
