How old are your Guineas? My first Guineas were scared to death to go out of the coop for months when they were young and first introduced to free ranging, but with increased exposure and time, they came around. Now, I usually let my hens hatch their own so the young keets free range from just a few days old and I don't have any problems with it. It sounds like yours may be adults, though. In that case, you may have to force them to go outside each day and gradually increase the time they are out each day till they are not so freaky about it. Hopefully others on here have more to add as far as advice goes!
They are 6 months, I believe. Thanks, I will keep kicking them out every morning.