As mentioned, if you bought cold hardy vs. warm tolerant chicks that may sway how they adjust, but that being said I would let them adjust to the temperature changes on their own and they will do much better. I live in NW Indiana, so, well..........Indiana, but I have always read and talked with chicken people that the birds without provided heat do better (sickness, temp changes, etc) Chickens do make their own heat, and do a good job. As long as they are in a sheltered, draft free area with ventilation, they should do fine. Also, if they are used to heat and for some reason lose it (power outage) they may do worse than having adjusted on their own. As for your lamp if you choose to heat, if it is infra red for animals and hung correctly you should be fine. Enjoy