I am a musician; I play piano very well and do a lot of accompanying work in my city. I am fairly in demand to play for OF Masses. I have participated in the Traditional Latin parish choir as a singer.
A couple of things for you to think about.
First, I appreciate that you are asking for suggestions. Good for you!
I assume since you are planning this program that you are the conductor and that you have a solid music education and experience?
If not, is there a conductor or choir director who is educated and knowledgeable about the traditional music styles, and who is with you all the way on this plan?
If not, you are going to face a real struggle. This is some heavy music.
Also, as others have kind of asked–is this kind of program the norm for your parish? If this is the kind of music that the congregation is used to hearing, then your Mass music will be ethereally lovely and the congregation will enjoy it and benefit from it. Congratulations and best wishes for a beautiful Mass.
If this is something new, then you had better make absolutely sure that it is of high professional quality or you will have a mess, not a Mass.
People don’t mind being nudged out of their comfort zones, but no one likes to be blasted out of their comfort zones and dumped in a totally foreign place.
If this music style and repertoire is new to the congregation, my main suggestion would be to make sure that you have hired the best cantor, choir, and organist or chamber orchestra in the city so that the congregation will have a good impression of this kind of music and go from the Mass wanting more.
If your cantor/choir and organist are not top-notch, or at least have practiced to the point where they can really give a good performance of these pieces, the congregation will hear limping, puny, foppish music in a foreign language instead of the magnificent pieces in the Church’s official language that you are envisioning in your mind. There will be complaints in the parish office about the music, and the priest will never allow you near the Mass music again.
So do this right.
I am a bit concerned that you are planning this music only a few weeks away from the Mass, unless this is the kind of music that your cantor, choir, and organist is used to. IF they’re used to this music, then you’re probably fine.
BUT listen to me here–if this is all new to the musicians, then you would be better to plan this kind Mass music for three or four months from now and let the musicians spend a lot more time practicing it, unless, of course, you have several evenings a week every week set aside for rehearsal from now until 5th Sunday of Easter. This is tough stuff. The repertoire is much too difficult to do in just a few weeks. Most choirs who are new to this kind of music, unless they are very very good musicians, could not learn this in only a few practices. Same for the organist–if they are really good and experienced, this music would be fine. But if your organist is used to playing folk hymns and traditional praise hymns (Holy God We Praise Thy Name, etc.), then they will be confused, and if your rehearsal keyboardist is confused, the singers will be even more confused, and that will be disaster.
I’ve seen really good choirs struggle with pieces that should be fairly straightfoward. If they are new to this, you have to train them in all aspects of the music, including the intonation techniques, or you will end up with a “country-western” style of chant, very unpleasant to hear.
So please do this Mass right, OK?

Make it good!
If this kind of music is new to your
congregation, do not make ANY assumptions about their ability to sing chant easily, or to easily read Latin, no matter what you have read on this board or on any traditional website or blog.
Assume that at least half or more of the people in the congregation have NEVER sung chant or Latin (born post Vatican II, and also all the converts), and that the other half is old enough that their voices are crackly and that they don’t remember this kind of music clearly and they hated it back when they did sing it. That’s reality.
Don’t let your imagination run away with you and envision a gorgeous Mass with all kinds of finely-dressed people singing enthusiastically with tears of joy streaming down their faces that finally the music is reverent again. Force yourself to think realistically–most people will be wearing jeans, most people will stand there and not sing, and most people are not interested in traditional music. (They COULD become interested IF you and your musicians do a great job and “sell it” to the congregation.)
Do not assume that “everyone loves traditional music.” (I personally don’t like it, and I would not attend a parish that regularly did this kind of music.) Be brutally realistic and reduce your expectations about what your congregation can do and will do and will like. Plan for the lowest common denominator (someone like me

) and PLAN to sweep us off our feet with the beauty and grandeur of the music and change our minds and make us want more! (Perhaps one reason why I dislike this kind of music is that it is generally so very badly done.)
Best wishes to you, and I’m sure everything will work out fine.