I don’t see a reason why you couldn’t go. Seders are a Jewish tradition, not a Catholic one.
Just be aware that the a seder led by a Messianic Jew is likely going to have been Christianized in some way. I’ve been to seders led by Jews for Jesus myself, as well as seders at my former Protestant church that were put together by a Messianic Jew who was a member of that church. These types of seders definitely can have many Jewish elements, but are not identical to the kind done on Passover by “regular” Jews (IOW, Jews who don’t believe Jesus is the Messiah). The latter lack the “Christianized” elements.
If you ever get the chance, you might check out a “regular” seder sometime to see the difference between the two.
Personally, I don’t go to these “Christian” seders anymore myself. I realize that the people running them/attending them mean well, but for reasons I can’t explain, to me they tend to come of as gimmicky and disrespectful. But for Christians without my Jewish background, it could be an entirely different thing from the way I experience it.
Enjoy!