If by "how beautiful" you mean Twila Paris, please, no.

I wouldn't propose ABBOT'S LEIGH for a wedding congregation. I know organists adore the tune, but if Love Divine and All Creatures (the OP already noted LASST UNS ERFREUEN drew a blank from the couple) are terra incognita, ABBOT'S LEIGH is far more remote than those for Catholic + unchurched congregations.

Frankly, if they are THAT unchurched, I’m not sure they should get that much of a say. Sounds harsh, but let them pick the marching music and then select the hymnody yourself. No one but the cantor will be singing anyway.

In any case, any of those texts could be paired to different tunes.

I wouldn't pick any of the ones I listed either. It's just an answer to the question of what might be recognized by the couple in question.

In fact, at funerals at least in my old parish, the DM would do the gradual unless someone insisted.

I would take the same approach for weddings if possible.

I have no compunctions about ending a hymn after verse one if no one has joined in yet. I might make an exception for "A mighty fortress" of course ;-)

I'm in agreement with you all completely. I yearn for better music. They've insisted on their requests to the point that I'm willing to do music that I would rather not just to get by.

A family that has mostly left our parish (which is sadly a common reality in this town) because of the shift to a reverent Mass and the music that goes with that, a couple that doesn't go here, a substitute priest, an embittered cantor (aunt) only singing because they insisted, and two weeks to get everything together.

Here's the list I sent (and yes, I tried to bury worse pieces at the bottom of each list):

Offertory:
Love Divine, All Loves Excelling (or Alleluia, Sing to Jesus, which is the same tune)
O God Beyond All Praising
Joyful Joyful We Adore Thee
Holy God We Praise thy Name
Praise to the Lord, the Almighty
At the Lamb’s High Feast We Sing
Lord of All Hopefulness
Shepherd Me, O God? Maybe? This strikes me as more of a funeral piece.
Where Charity and Love Prevail
Prayer of Saint Francis (only because it was Grandma's favorite piece)

Communion:
Gift of Finest Wheat
Love Divine, All Loves Excelling/At the Lamb’s High Feast/Where Charity and Love Prevail could also work here.
Taste and See, Moore
Ubi Caritas, Hurd (this could also be offertory)
The King of Love My Shepherd Is
God is Love, Joncas (at least it's close to the Ubi Caritas text...)

"Frankly, if they are THAT unchurched, I’m not sure they should get that much of a say. Sounds harsh, but let them pick the marching music and then select the hymnody yourself. No one but the cantor will be singing anyway."

Serviam Scores said this better than I could. IF singing a hymn for weddings or funerals is important, then you have to sing it at least 6 times during weekly Mass in a year, so at least those who attend Mass regularly will sing it.

Otherwise, create a small choir with a set repertoire and sing that music unchanged at every funeral or Mass.

The TLM does not have this problem. What a concept! The person that superimposed Ave Maria on Schubert's secular song must have needed income as a soloist at a Latin Mass.

then you have to sing it at least 6 times during weekly Mass in a year, so at least those who attend Mass regularly will sing it.

My parish tries anything once. The kicker is that some hymns, particularly the more nineteenth, early twentieth-century kind that we've largely dumped from the repertoire, are just too hard. But we could probably try something like "Lift Up Your Heads, Ye Mighty Gates" (MACHT HOCH DIE TÜR, please) once a year and get everyone hooked on the second or at least third verse…

A pity. I don’t care for TRURO, which rings as too Episcopalian for me. That was a problem in an old parish and to some extent here. New words or tunes were okay, but the tunes had to have oomph without feeling Episcopalian to cradle Catholics or the longtime converts.

genuinely not knowing what sacred music is or should be

which is why I'm generally fairly strict with funerals. Ahhhh the folly of allowing people who have never studied liturgy or theology dictate the liturgy....

Like the quintessential parish volunteer boomer lady who has totalitarian control of all parish funeral planning?

Of course! Let's have a "ressurrection celebration"! (can never remember if two ss's or two rr's so spelling with both... in your mind, delete the letter that does not belong and be happy)

NOTE: Don't build bridges to OCP (sandy ground)

any old text to THAXTED - I'm sure there'd be a marriage-specific one somewhere

O God Beyond All Praising gets done for weddings a fair bit hereabouts.

Serviam: that Victoria adaptation is slick!

there are also just more options than an annual dealio for that.