The following thread is an excellent read through for anyone preparing to process for the first time - or really anyone processing.
https://www.backyardchickens.com/t/777712/most-important-aspect-of-butchering
Another thought is to process perhaps a quarter of them as Cornish game hens at about 3 1/2 to 4 weeks.(which is what I do) That makes more room for the others and makes the last processing less daunting.
It probably won't happen in a day.
At my house it is usually just me and I limit myself to about 4 at a time.
A means of keeping the water hot, like a turkey fryer, helps a lot. If you're doing it often a plucker is the way to go but they're pricey.
Think about how much help you'll have processing that many birds.
Poultry netting will be scoffed at by most predators. Meaties aren't fast are are easy prey.
Buying in bulk is the way to go for cost.
Long grass isn't delectable to chickens. New sprouts are. So I'd either mow the area just...