I wish I could be of more service here; but time is of the essence. I know this is probably too late for you to take advantage of anything I say. There isn’t any conflict with your vegetarianism, regarding eating; though the seder requires a bone (roasted beef bone or neck of a fowl) to represent the pashal lamb. Maror (bitter herbs) is horseradish and other components are fruit , vegetable and unleavened grains. You only need apples, nuts, honey, grape juice/wine, cinnamon/nutmeg and lemon peel/juice for the charoset, which represents the mortar. Karpas-a green vege, like parsley or celery; lettuce (charzeret) and a roasted egg, reminder of the regular festive sacrifice at the Temple.
Here is a Messianic Prayer Book (siddur) that contains an entire Haggadah. Although there are just a few actual commands for Pesach:
Ex. 12:15- cleaning out the leaven in your homes (literally and figuratively),
Ex. 12:15-20: matzah,
Ex. 12:8 and Num. 9: 11: maror(bitter herbs) and the lamb meat itself (Ex. 12), though the Ashkenazi in the Jewish community generally do not eat lamb a this time since there is no Temple, but other Sephardi will.
The additions by the rabbis through the years are very worthwhile and carry significance. It is a “telling” (meaning of Haggadah) using an “order” (seder) of service to teach and tell.
One thing that bears mentioning, and I hope it doesn’t offend anyone. I would ask that when referring to the Seder, please be considerate of your Jewish brethren who find it sacrilegious to refer to it as a “Christian seder”.
Keep in mind, that to Yeshua (Jesus), it wasn’t a Christian seder. He brought forth symbolism within the seder of himself, but Passover isn’t either Jewish or Christian; it belongs to G-d (Lev. 23) and all His People can participate according to Torah. However, the seder is a Jewish custom based on the Torah (hence Yeshua’s observation), not a Christian one, so I just ask that there is some respect to that historical truth that is such an important component to their identity. I hope you understand, I know no one was intentionally trying to be offensive; sometimes we just don’t realize the effect our words or phrasing could have another people group; I’m not trying to be PC, but promote respect. I hope that comes across.
Just do the best you can this year since its last minute and there’s always next year to plan ahead.
Rachel