It happens to me every year. I think to myself “I’ve done this before,” (we’re not counting how many times). While I wouldn’t claim to be an old pro at the Passover Seder, I’m not exactly a neophyte, and I know without looking to prepare salt water for dipping and the rest of the trimmings. However, there is always something (or two things or three or five things) that catch me by surprise as if by the first time. Once, I will confess that I nearly forgot the cup for Eliyahu until my 3 year old graciously reminded me. Even though I didn’t see the great prophet eye to eye, I sensed my son felt very grateful.
It is said that one should review the laws of Jewish holidays a month before the holiday. This is a great precept, although I still have yet to crack open my Haggadah (book used with the text of the Passover Seder, or special meal with rituals, stories, explanations and songs). Fathers and sons in very traditional families spend the time from Purim to Pesach poring over the text and discussing its complexities (and there is much beautiful simplicity in the text too, for those of us who are not experts).
On Shabbat HaGadol, the Shabbat preceding Passover, our tradition is to read portions fo the Haggadah as preparation. So there are many opportunities to get ready f the big seder. Try reviewing portions with your children. This may be simple or more elaborate depending on the ages. A good place to start is “ma nishtana” “Why is this night different from all other nights,” (a series of questions), the four sons, the actual narrative of leaving Egypt (little boys especially love graphic descriptions of the plagues), and the songs at the end. You can also introduce them to the order of the seder while reviewing it yourself.
You can find all kinds of Haggadahs in Judaica stores or online. Many are available with English translations and there is also a wide selection for children. Read, rehearse the seder, and enjoy!