20 drones.. I'd estimate around $500 per drone perhaps, then the software to control them (unknown cost, probably a few hundred $$) expertise to program them (external source $$$) learning yourself - free but probably a very steep learning curve. Licensing to use aircraft probably in the dark in...
You are likely to be better off hiring a crane to hold a matrix, drones require batteries to stay in the air for a very short amount of time, even less with a load suspended from them, those batteries require charging which will take away time from being able to run your lights, unless you have...
Beginning to think I'll need a cherry picker at some point.
Rj45 crimpers and crimps are something I'll always have on hand.
Multimeter for sure
Thermal camera to see if there are any obvious issues before they become bigger.
Various ladder sizes and straps to tie them against something if I...
Depending on how big the load is, could you use one of those portable power stations, they often have a "UPS" mode, double use as a portable power solution for camping, travelling etc outside of the Christmas season, and will run for longer than a standard computer UPS will.
You will find a lot of users here would suggest that you don't go down the Wi-Fi route, as cable is king when it comes to light shows, you won't experience stutter, lag, latency, dropped frames with a cable, however you are likely to with Wi-Fi. If you really must, you could try a raspberry pi...
WiFi is best to be avoided if at all possible when running larger numbers of lights, if you can hardwire to your controllers, you will get a more positive experience. Wifi boosters only boost what they can get their hands on. If they get a bad signal, they'll be boosting that bad signal.
Most floodlights won't do much till it's dark, could try the 30W ones from Ray. I searched for "Flood" on his store page, came up with a lot of results that could work for you...
Has unplugging everything and then plugging back in potentially triggered them to get new IP addresses from the DHCP server (probably your router) assuming nothing was set to static before hand.