well that is not surprising since it is a Jewish celebration, not Catholic. First find out if such an endeavor is permitted or encouraged in your parish or diocese, as there are some strong feelings about it. A video about passover, especially one showing the links with the Last Supper might be more doable. In our former parish, in a neighborhood with a large Jewish population, our pastor discouraged a parish or CCD seder because it offended some of our neighbors, who evidently saw it as a “mock” reenactment of their own rituals. That is legitimate and should be respected, as should any attempt to “fake it”.
If it is permitted, decide how much of the prescribed ritual you will be doing–are you going to roast a lamb for instance? Wine? Look for books in the children’s section of the library that describe Passover, the preparation, the meal, the reasons for the elements of the meal, the prayers and so forth. You can often find this time of year in the ethnic section of your chain grocery store, or in a kosher market if you are lucky enough to be near one, little pamphlets that give the order and prayers in English on one side, Hebrew on the other.
it might be a more valuable learning experience to focus on the Passover story, and the elements of the meal and celebration that are significance, perhaps have a sample of the foods and discuss their meaning, some of the blessings, the place of Elijah etc.
I would not try to do to much discussion relating it to the Mass at this lesson, but develop that link in future lessons.
there is a CD out with songs in ancient languages Ancient Echoes? I think it is that has some of the blessings and songs.