Hi,
I think it would be safer to keep them in for a bit longer,at least until they are 6 weeks old.
I would start whilst they are in the shed,giving them a bed time treat,call to them using the same words each time,and then scatter/feed them the treat.
It will help once they are free ranging,close to dusk you can stand at their home,call them and they will all come running.
If you have some that are good fliers,and have plenty of trees,some may decide they prefer roosting in a tree,and if up high enough,should come to no harm.I'd expect this to happen though,when they are more mature,not straight away.
To start with,have their water containers close to their home/house,they will come back to it for their water,food and security.
Ducklings/ducks are a bit different,wait for Tim's advise for definite on that one

.