After two years with guineas here's what I have found.
I got 7 guinea hens as keets last spring. The were brooded along with a dozen chicks and did just fine--I brooded them in half of my chicken coop, separate from the adult birds. They did fine on a diet of game bird grower. When both species were about 5 months old I let them out in the big room with the adult chickens which meant they also could go out into the chicken yard. At first some of the guineas returned to the coop to roost, some didn't. I tried to round up those that didn't with mixed results--one flew over the fence and disappear, presumably eaten. Eventually the remaining 6 got the idea and roosted in the coop every night, generally going to roost after the chickens. (They also laid eggs on the floor of the coop.) In October when the birds were 6 months old I opened up the gate to the chicken yard to allow all the birds to free range--I also open up the garden at this time so the birds can clean up bugs and weed seeds. The guineas wandered over my property and, occasionally, on to my neighbors but stuck fairly close. They all returned at night but I had to be sure they were on the roost before locking down the coop.
About this time 3 cocks that belonged to a neighbor who lives about half a mile from me showed up. These had been part of a flock of about a dozen birds but were the only ones remaining. These cocks hung with my hens all winter--usually the cocks roosted in the trees in my hedgerow even when the temperatures dropped to 30 below. The hens, however, continued to go into the coop each night. I was concerned that maybe the cocks would lure my hens away but the opposite was true. When I stopped in to the neighbor to tell her where her birds were she told me they'd come home. get something to eat and disappear. This went on all winter and well into the spring. We have 3 fairly open acres around the house, a mixture of lawn, hedgerow, hardwoods and fields. Both sets of birds stayed close but not as close as the chickens.
This led to their eventual loss. Within 2 weeks at the end of June some predator--I assume a red fox--began picking them off one by one. Leaving only 2 of the cocks who, after the last hen was taken, continued to show up each morning calling for the hens to come out. I have discovered that guineas rely on flock numbers as protection from predators. While both the chickens and the guineas were free ranging in the same area, I only lost one chicken during this time. In fact, I spotted the fox only because my two roosters put up such a fuss that I came running just in time to chase it off. On the other hand, my last hen disappeared within 30 minutes of my last seeing her with one of the cocks and there was no indication there was a problem--the cock was fine, still is. Of course guineas are noisy so it is hard to tell if there is a problem or they just can't find each other. From reading about other people's losses I suspect this is a fairly common occurrence--guineas don't seem to have a real high predator avoidance strategy.
Now as far as ticks. We have 2 indoor/outdoor cats. Both are fairly old and don't wander far from the house but I do know they get into some of the wooded area on our property. Now cats are fairly good about keeping ticks off themselves except for their heads and shoulders. One of the reasons I got guineas in the first place was I was tired of pulling ticks off the cats' shoulders, necks and faces--worst are the tiny nymphs that get around the eyes. While I kept the guineas fairly close last year and found ticks on the cats into the fall, once the birds were out and about this spring the ticks seemed to disappear. (We have a herd of 6 deer that hang around so there is a steady supply of deer ticks.) While I am certain the chickens will take ticks as well, the guineas seem to get into areas where the chickens will not go--another reason for their contact with predators. I have not found a tick on either cat all summer so it seems to have worked. Also I watched the guineas actively hunt Japanese beetles and ants so they're good for controlling other pests as well. Now we'll see if ticks make a comeback since the guineas are gone.
End of story: I now have 16 keets that I purchased from Purity the first week of August who will be free-ranging later this fall and, hopefully, next spring. I'm hoping the numbers will be helpful in keeping a few around long enough to discourage predators and ticks.
Hens go broody when you don’t want them to… and won’t go broody when you do. 
