While we don't like to state the obvious, we'll state the obvious: The Merchant of Venice is a hornet's nest of controversy, from latent homosexuality (nothing obvious, but the friendship between Bassanio and Antonio is frequently seen as more than friendship) to the over-the-top anti-Semitism in the depiction and treatment of Shylock.

Why are you teaching this play? Part of the mandatory curriculum of your district? You still have to be able to defend the work as worthwhile literature. If you have flexibility in what your class studies, make sure this is the right work for you and your class. There are better Shakespearean plays and certainly better comedies. However, if you are interested in challenging the way your students think about prejudice, social mores, and the status quo, this could be the right work for you. So gird your loins and get going.