Where do you have these three-week olds? Have they been raised indoors in a brooder box or are they now in a coop and have access to the run? Are they under a heat lamp during the day still?
Do you plan on letting them out to run loose or are you just wanting to let them start having outdoor playtime in a protected run?
Three-week olds will be frightened of being turned loose to free range without adequate cover, so I advise against that. And you must choose a mild weather day if these chicks haven't been acclimatized to cooler temps yet.
We currently have them inside the house, in a horse water trough, under a heat lamp, they are on shavings, they eat organic chick starter ...
We have 2 Golden Laced Wyandotte 4 Silver Laced Wyandotte and 2 easter eggers
We initially got 6 then decided a day later we wanted 2 more
we live in Washington state PNW Pacific North West...
I was just wanting them to see the out side, I guess I will wait till they are ready in a few more weeks... I surley wouldnt want anything bad to happen, I was also worried I wouldnt be able to catch them...
Short field trips outside on mild days are good for them. But they will feel more secure if the area was protected at first. Chicks fully realize how vulnerable they are to predators and they won't want to run far and wide for the first week. Just fence a small area of soil for them to scratch in, protected from cold drafts.
At three weeks, they should not need heat during the day, so turn off the heat lamp and let them adjust to not needing it during the day. In a few days, they will then be ready for their first trip outdoors. Just watch them for signs of chilling and bring them back in.
You should spend the next couple days while they are adjusting to no heat during the day to train the chicks to come to you. I like to use a clicker as an audio cue or you can use a word, start getting them to associate coming to you on command with treats.
It doesn't take long at all to train chickens to come. No one ever needs to chase and catch chickens. They are very willing to come when they think a treat is their reward.
At age three weeks, if the ambient temp is around 70F, chicks are feathered out enough to where they will lose no body heat at that temperature. That and the fact that they are eating and replacing lost body heat by converting food calories to heat.
They will continue to need declining amounts of heat at night for a couple more weeks for the simple reason they do not eat at night, therefore do not consume calories to convert into body heat. After they are completely feathered out around six weeks, they are completely insulated against heat loss, even at freezing temps as long as they've been gradually acclimatized.
Took my three outside for lunch today. 2 are a week old and one is 2 weeks old. They are in a cage, not box. Set them in the sunlight by my coop with hens and let the hens range around them. They had a ball. Jumping in the air for bugs, checking stuff out, pecking at stuff. Dropped a couple small roaches in for them to eat. Came out an hour later and they were piled in a ball in the sunlight sleeping. Temp was 65 degrees. I say the sooner the better as long as its not cold. I'll take mine out pretty much daily now. I especially want them to be around the hens as much as possible leading up to the integration.