I'm no expert, but when I got mine, I was told they were 2 weeks old, mostly feathered and could fly (One escaped but was easily caught) ! There were about a dozen keets in this cage in a barn and didn't have any heat.
For your keets, when they're fully feathered, which is around two weeks, I would lower the temp about 5 degrees per day, (raise the lamp) watch to see if they huddle too much, smaller ones can get hurt (or worse) if the pile up on each other.
Once off the lamp for about a week or two, which would make your birds around 4weeks old, some people keep them in an outside brooder, something separate from larger birds, but still able to access a run, but more shelter so they don't get wet.
Depending on what temperature 'chilly' is in Arkansas, a lamp might be also be used outside.
Not sure where you keep them right now, or how many keets (in a spare room, or in a barn, and 12keets can generate more heat than 2) but how ever you do it, it should be a slow transition.