Help with networking event site - SOHO MK3 and APs

Quick background: Iā€™m a stoopid designer. :wink:
Goal: ad-hoc network for file transfers and printing network.
Equipment: SOHO MK3 - AP Rugged - AP ONE ENT

I work at remote events backstage and would like to network multiple computers backstage and possibly extend to computers 300+ feet away. Primarily for file transfers (LAN or WAN) to multiple computers from a backstage server/storage to eliminate USB sticks.

Would like the network to NOT rely on any internet connection. If an internet drop is available, then it could be ported into the SOHO.

Backstage: could be connected via ethernet but would like a wireless option as well.
Operations: usually located 300ā€™+ away from backstage. This would have to be only wireless as producers, directors and clients are always moving.

My question is I need advice on how to setup the SOHO <ā€”> APs <ā€”> Server.

Diagram is attached to help visualize. Thanks so much!

network diagram|690x388