Ken;
Few of us have the patients to start trees from seed. Another problem is, the fruit, if they eventually fruit, will rarely match that of the original tree. Persimmons have both male and female trees, if you're 'unlucky' enough to end up with three male trees... you'd have no fruit.
What I'd consider those trees to be is
rootstock, the non-fruiting portion of every fruit tree that dose the job of anchoring it within the soil, gathering nutrients, and limiting the eventual size of the fruiting portion above. Though seedlings of Fuyu 'are' closely related to the 'fruiting tree,' I suspect they could also be used successfully as rootstock.
As far as growing these 'seeds,' I think you're on the right track with a deep pot (bigger's always better), or just set them into the ground. I'd bury them just below the soil line and expect them to send down a tap root, and up with a sprout! If you've got 3 pots, you might vary their exposure to 'your' sun, but around 'here' persimmons love full sun and heat.
I have 4 persimmon trees, but with no males, never get seeds. I have ordered native persimmon seedlings and used them as rootstock to graft fruiting varieties to. I'd assumed my grafts had failed as they went most of the summer showing no growth, until very near Fall - then they took off! Now they reside with family and friends, each fruiting like the 'real thing!'
If I were you... I'd plant those seeds in the deep pots, let them grow this season, and either bud (graft) a known variety {you've got Fuyu handy} this fall, or, 'splice' graft when they're dormant. Persimmons make beautiful specimen trees because of their size, shape, and foliage, but if you're missing eatable fruit - you're missing eatable fruit!
Let us know how they fare; they're my
favorite yard tree, and one of my favorite fruits
