Hello!
As far as weather to free range them or not, if you decide to, you should keep them locked in their coop for a couple weeks so that they will start to think of it as "home". When I first joined BYC, I wanted to know more about free ranging so I started
this thread. A lot of people chimed in and gave some great opinions/experiences on it! Right now, we let our free range part of the time, but only when we are paying attention. We plan on letting them do more so in the future, but we are still working on securing up their winter coops right now. We also have hawks, bears, coyotes, foxes, etc, etc, etc. We haven't done it all day yet, we have started with a couple hours at night so that they don't go too far, and it is easier to keep an eye on them. They have done great with it so far though (though... I have had two chickens land on our house!

) If you let them free range, and you have a garden, make sure you have your plants protected or they will eat the leaves and fruit of EVERYTHING! They are pigs.
How far are the chickens from you now? If they are from another state, or even on the other side of the same state, the soil from where they are now is different... which means the coccidiosis in the other soil is slightly different, and even if they are immune to that, you will want to build up their immunity to the cocci in your soil. What we do to do this is not put them immediately outside when we get new ones. We keep them in their coop for a few days and give them herbs to build their immunity to it (oregano, garlic, and aloe juice). And then we start giving bits of dirt and grass to eat, so they can slowly work up their immunity and it won't be too much of a shock to them. Not everyone does this, but we have just to be safe. If you want to learn more about treating chickens and keeping them healthy with herbs, I have an
article on it.

I'm not an expert or a vet, but these things work for us!
Good luck with your chickens! This is a great community for learning more about them and how to care for them!