Which French literature is it that you think might be thought 'scarry'? Messiaen? Litaize? Langlais? Tournemire? Some might think one or all of these and their colleagues frightfully modern and unpleasant. Others would not. I have had people tell me after recitals that included Bach and baroque pieces that their favourite piece was the Messiaen. Never fail to challenge people and give them credit - and broaden their horizons.

Having said that, some relatively tame French literature would be the works of the XVIIth and XVIII century composers. Look into the various movements of their organ masses and magnificat suites. These make wonderful voluntaries before and after mass - or during the offertory if you play the organ then. Names to look for would be Titelouze, Lebegue, de Grigny, Raison, Clerambault, Couperin, Corrette, Marchand, and so forth. Most of the organ versets in their works are relatively short and are easily combined into little two or three movement suites to serve as a very fine voluntary before mass. Others serve very well at the offertory and during communions.

There is a fear suffered by some organists that mass music (especially from the organ) must always be quiet, unobtrusive pablum. This is not so. It should reflect the tone of the day's celebration, whether meditative, prayerful, or joyous and exuberant. Aiding in communicating the tenor of the day's import is your goal as an organist. (And don't be too upset if one or two people have the ingratitude to complain about something that you played - think of all the two or three hundred others who didn't complain. They very likely either liked it or were indifferent. I have on a number of occasions had people come to me after I patiently listened to a complainer and say something like 'don't mind her [or him], we like your music'.)

I can't see Dracula in your example. More like the profound mystery surrounding the Godhead and the serene beauty of his house.

The problem with Baroque organ music in a minor key (apart from anything that is obviously a minuet or a gigue) is that blasted d minor toccata by Bach (or not by Bach, depending on whether ot not you agree one scholar or another). That has been so overused in bad horror movies or Halloween skits, that anything akin to it makes the great unwashed masses think of Dracula. We organists may hear "lovely French Baroque prelude in g minor/mode 2", but the rest of the world will hear "Halloween". Yes, it's stupid, but, hey, that's life. (Vel, "Oui, c'est stupide, ah, c'est la vie.")

That has been so overused in bad horror movies or Halloween skits, that anything akin to it makes the great unwashed masses think of Dracula.

Musical illiteracy strikes again.

Try something by Jeanne Demessieux. There is a very useful collection published by Summy-Birchard, called Twelve Chorale Preludes on Gregorian Chant Themes; obtainable from Amazon. Listen to this one, based on Rorate Caeli:
https://www.youtube.com/watch?v=Lvm_QlKraJE
This is the easiest one, some are more rousing and they cover most seasons of the Church's year.

Don't forget "Ten Chant Preludes for Organ" by Gregory Hamilton.

Thanks everyone for the great suggestions! Feel free to add more if you think of them!

You can never go wrong with Flor Peeters.

...can never go wrong with...

I've never liked Peeters' music at all.
I am aware, though, that he does have quiet a large following.
If I never again hear his (incredibly gaudy) Entrata Festiva I shall remain joyful.
Aeons ago I was at a parish at which that was the default piece for every special occasion..
It's not that his music isn't good. It is. It's just not interesting.