Joe Paprocki has some serious concerns about Catholics celebrating a Seder Meal that I think are worth reading. His first point is the strongest:

First and foremost, the Seder Meal is a sacred Jewish ritual. For Catholics to re-enact this sacred ritual is disrespectful of the Jewish tradition. (Imagine Jewish or Muslim children re-enacting a Catholic Mass, complete with the giggling and awkward moments that are part of any children’s production). The Seder Meal is a Jewish tradition that Catholics should enjoy only if we are privileged to be welcomed to a Jewish Passover table.

Read his entire post here.