Complex sentence: The Glee Club is currently in the midst of planning its 150th anniversary celebration, which is to include a large-scale cross country tour and an appearance at the Ravinia Festival in 2008.
Split into simpler sentences: The Glee Club is currently in the midst of planning its 150th anniversary celebration. This celebration is scheduled to include a large-scale cross country tour, cumlinating in an appearance at the Ravinia Festival in 2008.