They don’t usually attack if you’re right there, so I’m sure you could move the girls from the coop to the tractor without too much trouble.
You may have hawks that live nearby but since this was your first attack it could have been a transient bird, or by the sounds of it a pair looking for a new territory. Like most animals there is a good chance they’ll lose interest if a food source is no longer available for a few days or a week but even so, they’ll remember and could come back now and again to check
They don’t like anything in the air with them or in the way however, so things like a flagpole with a large flag, a clothesline etc can help. There’s also hawk-shaped “kites” that you can mount on your roof or on your coop and they “soar” in the slightest bit of wind, they can deter hawks, pigeons, gulls etc.
I had a lot of luck keeping a duck with my flock, they’re hyper-alert to threats from the sky, and the chickens learned to run and hide when the duck quacked a warning about hawks.
Good luck!