We just let out our 9 week old chicks - had not planned on it for a few more weeks but after watching the interaction - I am very pleased so far. We kept them in the house until feathered out and moved them to a brooder/grow pen in the coop. Ours free range during the day and are locked up at night so the real interesting test will come in the morning when they are released for the day. Based on my experience, your chicks should be fine.
Shelly
Shelly