Another term for saying "Opener" in a Christian devotion.
The opening prayer in a Christian devotion is usually called "the invocation". I have never heard the term "the invocator". I have heard, "She will lead the invocation" or "He will give the invocation".
precentor - a person who leads a congregation in its singing or prayers.
cantor and chorister are other words you might wanna consider.
cantor - 1.choir leader 2 : a synagogue official who sings or chants liturgical music and leads the congregation in prayer
chorister - A person who leads the singing of a church choir or congregation