Guineas like to roost 15-40 ft in the air, not 3-4.
Guineas would not take kindly to being moved like a common chicken in a tractor.
They do great in a garden if allowed to come and go. Guineas are contrary birds. they will like anything you do not want them to like.
They will attack other birds, dogs, cats and almost anything. They are fearless.
They really need a lot of room to roam. A tractor would not be good for them.
Read this ad from Craigslist. It is not mine but I got a chuckle out of it
http://minneapolis.craigslist.org/csw/grd/5918291881.html
I am not sure you are prepared for the guinea adventure. When Breeding season comes Guinea behavior goes from contrary to rude, mean and dangerous to other critters.
There is a person on here @BantyChooks Talk to her about guineas. She had them for a short time. Many people have them a SHORT time.
How close are your neighbors? If it is not 1/4 mile or your neighbors do not mind the noise I would say do not get them, I have seen mine over 1/4 mile from the coop. Training a guinea does not happen..\
Sorry if this seems cruel but it is a fact. I have a friend that got guineas from me, until they decided to have a turkey dinner. A turkey is no match for guineas... They are the piranha of the bird world.