From my own experience growimg bananas and fruit trees in my garden:
I planted bananas at certain spots in the garden. One place was 10ft away from a young lychee tree to create a green wall against winds that lychee doesnt like. I did heavy mulching and chop and drop of banana leaves, stem that fruited and lychee is happy.
Another place banana i planted under the shade of an oak, did well but didnt flower well, so banans don’t seem to like shade as much as full sun.
Another was close to avocados and avocados love mulch so do bananas, avocados don’t mind some shade. But i am worried the avos will eventually shade the banana in time.
You can plant banana close to the young trees, 12ft is ok in my opinion and once tree grows big remove the bananas, as it will shade the banana and won’t produce well. Black sapote, Mamey, avocado all will grow into huge trees. I have been growing banans for last three years here in south florida, lot of mulch, chop and drop, never fertilized or watered snd they are disease free and very good tasting.
https://youtu.be/Wk8ibxAAqr4