Would you go individual or trust in this situation?

[georgeib]

If you want to add another NFA item to the trust at a later date, would they all have to go through the background check for the new item?

No, because you have added them with an addendum page that you will remove while applying.

You can add and remove people from a trust at will. In Georgia, it isn't even necessary to get the addendum notarized. So you add a page to the back of the trust with any additional trustee or beneficiary, and remove that page(s) if you would like to remove that trustee(s).

ETA: Alternately, you can have the additional trustees and/or beneficiaries in the trust, and then use an amendment page at the back of the trust to remove them for the purpose of applying.