They really do look too young to be put outside, they aren't feathered out enough at all.
I have some older than that and they are still in my living room.
I start by taking away the heat lamp but still keep them in the house.
Then I move them to a big brooding pen in the garage, if the nights are cold I give them back the light just at night until they start to gain some extra weight for warmth.
I move them to the coop between 10-12 weeks.
(but I have them in a good size pen until then)
I have 8 week olds still in the big inside pen and one month olds in the living room.
All of them go outside during the day for some free range time and to get them gradually use to the colder weather.
I think you need to do it gradually but they will be hardy that way I think.
Its tougher this time of year and its kind of a judgement call, raising the chicks during this season takes a little longer to get them use to the cold and out in the coop
You have good chickens for cold weather though, they are a pretty hardy breed. I have some myself.
It goes by so fast they will be in the coop before you know it.
But yours are still babies, there are no feathers on their breasts it will be a few weeks yet.
Pretty babies, enjoy!