Naturally Jesus would celebrate the passover being a Jew and under the Mosaic Law but with His resurrection that Law was fulfilled and the opportunity to become part of ‘spiritual Israel’ went out to non-Jews. Christians do not celebrate the passover but commemorate Christ’s death.
No, we commemorate Christ's death(sacrifice for sin) AND Resurrection. The death is only 1/2 the story and is nothing without the Resurrection.
Christ intended that his death be commemorated on Passover, the anniversary of his death. Many in the early church continued to observe Passover. In fact, Passover was not "officially" banned until 325 AD, when the The Council of Nicea officially said not to observe the Passover on Nisan 14.
After that those who believed in observing the word of God and not the judgment of men went underground and were labeled heretics for doing God's will.