Putting brooder outside

I'm interested in hearing thoughts on moving my brooder outside. I have a covered area where I can put them. The brooder is cat proof so I'm comfortable that it will be any other preditor proof as well. I'm going to place it near my house and I have a fenced in yard so I don't typically get any outside critters in my yard.

They were hatched on June 1st, so they are 3 weeks old now. Most are feathered out pretty well on their bodies...not their heads. I live in NC and daytime temps around here are in the 90's (already-ugh!)...so I'm not terribly concerned about them during day...however, night-time temps are in the low to mid 70's. I could run an extension cord and put a light on them at night if needed...but with 25 in the brooder, I'm thinking that they would probably be okay.

Thoughts???

Thanks!