Can I let 2.5 week old chicks play in the coop for a few hours?

Yes you certainly can as long as you don’t have adults to cause integration issues. If they get cold they will let you know by giving a plaintive chirp. It’s a distress peep or chirp that you will recognize.

My brooder is in the coop to start with. I heat one end and let the far end of the brooder cool off as it will. On really cold mornings I’ve seen ice on that far end, but the chicks stay on the warm end. Since mine are acclimated to the cold, I normally turn off the heat source when the lows are in the 40’s if the chicks are five weeks old.

It’s difficult giving recommendations over the internet when we all have our own unique set-ups and management techniques, but those chicks can handle cold much better than you might think. For 2-1/2 week old chicks, 80 is warm, not cold.

If you don’t have adults out there and you have electricity, you could move them out there now if you wish. Just heat one area so they can warm up if they need to and make sure they have cooler areas to go to if it gets too hot.