In short, we should note the following:
1) A seder is not for Christians. Just as a Christmas tree is not for Jewish people. The use of a Hanukkah Bush is a grave misnomer according to the rabbis in my local community. As Christians, we should hold Jewish rituals in the highest esteem and moreover, not attempt to Christianize them. This may in fact be looked upon as anti-Semitic when we do so.
2) The modern seder did not begin until 70 AD, after the destruction of the temple. And in some ways this was a reaction to and a resistance of the Eucharistic meal that we celebrate. Note the date here. Jesus would not have been able to celebrate what we know as the modern seder as it did not exist. Whatever ritual he did partake in, it was not this one.
3) It may serve to “write Jews out of their own ritual.” In other words, by holding a seder in a Christian church and to end it perhaps with our Eucharistic meal is at best a shaky proposal. The meal is for Jews alone and usurping it for our own purposes can be mistaken as a sign of our saying that their meal is not important and that our Eucharistic meal supersedes their ritual. However unintentional this may be, it is a very real possibility that it may be interpreted as such.
4) Lastly, it would be in good form for Jewish people to hold seders and invite their Christian friends to participate on their terms.
The article above makes one final point that I will quote here:
If we really want to understand the mysteries of Jesus’ last days, we might consider participating in the classic liturgies of the Great Three Days of Maundy/Holy Thursday, Good Friday, and the Easter Vigil. It is there, in the experience of the powerful liturgical traditions of those three days, that we encounter the meaning, depth, and power of our salvation. In the ritual of the Passover, the Jewish people recount their story of redemption. In the liturgies of the Great Three Days — and especially the Easter Vigil — the Christian community recounts and relives our story of redemption.
Each year I attend a seder that our local temple holds specifically for the entire community. It is a wonderful celebration. We, in turn, often invite the Jewish community to participate in various events, community service opportunities, and much more.