Young/small keets are quick easy snacks for all kinds of predators... they just aren't agile enough or predator savvy enough to survive long, and especially if they are not cooped at night. I keep mine in a predator proof coop/pen set up after they are 6 wks old for about another 6 weeks, so typically they are 12 weeks before they start free ranging. The 6 wks in the coop/pen helps to imprints that the coop/pen is their home/safety. Cooping the birds at night, every night in a predator proof coop/pen is their best bet for survival. They need to be conditioned to return to the coop tho, which will require some consistent effort on your part to establish a nightly coop-up routine.
A young flock of free ranged Guineas that have to scrounge for their food usually won't stick around. You'll want to provide food and water for them or they may wander off in search of greener pastures, and take your older Hen with them.