IMO... (and this is just MY opinion, based on my own personal experiences with my own flocks) keets really should not be let out to free range until they are 10-12 wks old, after they have been in a coop/covered run type situation for around 4-6 wks so they know where their permanent home for roosting is, and also so they can get a little familiar with the sights sounds and activities on your land before getting let out. They also have better chances of not getting taken by a predator at 12 wks old than they do at 6 wks. During the 6 wks that they are acclimating to their new home I always make the same call, whistle, sound etc when I'm refilling their feeders, waterers and when I give them treats so they associate the sound with FOOD. This is very helpful for getting them back in after you start letting them out. but you have to do it consistently. If you have a predator safe, secure covered run attached to your coop, letting them out in that while they acclimate will help, plus herding them back in is easy and they learn earlier on that they need to go in at night. After they are well acclimated with their permanent roosting home, it works best for me if I start letting them out for short periods in the late afternoons... I usually take their food away around noon, let them out about 3:30 or 4pm, stay with them while they are out and then herd them/coax them back into the coop/covered run for food/treats/millet etc right before it stars getting dark. Since they are a little on the hungry side, it helps motivate them to come running back to the feeder when I call them. I do this consistently, gradually building up to longer and longer periods of time spent out, until eventually I can just open the door, let them out and then call them back in the evenings and they come running or... best case scenario they go back in in their own.
This is just what works for me, I can call my birds from anywhere n my 10 acres and they will come running/flying to me because they know they are going to get some sort of goodies. There's always more than one way to deal with Guineas, and yes, some times keeping a couple in the coop helps, but more often than not it just causes the 2 left behind distress (again, IMO). But maybe you can take a little of what I posted above and work it into your Guinea routine. Best of luck.
