Concerning the Gloria:
While through-composed settings of the Gloria give clearest expression to the text, the addition of refrains is permitted, provided the refrains encourage congregational participation. (Sing to the Lord, USCCB)
Two things about that:
- Sing to the Lord has no binding force, as it was not submitted to Rome. It could have force in a particular diocese, if the Bishop there wants it to, but there is no actual authority in the document.
- Why would one voluntarily choose a Gloria that does not give clearest expression to the text?
I’m not saying that Mass of Creation isn’t permitted. If you change the texts where they are wrong (two words in the Sanctus and one word twice in the Agnus Dei), it is permitted. In congregations that are used to it, there is a comfort level which makes it hard to give up. However it seems a poor choice to use if the parish is not already accustomed to it.
And now to the original question: There are 5 English one-part masses in the Adoremus hymnal. I think one or more of them would probably be ideal, as they are one-part even in the Choir edition (where the hymns are 4-part).
Of course, if you want to avoid any troubles with changes in translation, you can always use some Latin/Greek chants for the Mass parts. They’re certainly not going to change. The Jubilate Deo Mass Referred to by Pope Paul VI as “the minimum chant repertiore for every parish” is available free, and printable, online. Here is a site with several printing options, including both chant and modern notation:
ceciliaschola.org/notes/jubilatedeo.html
You may find the Kyrie and the Agnus Dei in particular to be familiar. I know they were used in my church all the while I was growing up.
Good luck, and bless you for your courage and perseverence!
–Jen