we started with adults in July. we have a chainlink dog run we put the adults in (6 of them) and one escaped the run but stayed near by. we kept them penned in the run for 2 weeks, feeding the loose one outside the pen (because there was NO catching it.) after 2 weeks, we opened the run and let them come and go. we kept a full feed dish and water in the pen and another set outside the pen... we did not have any wandering off.
we have lost a couple to predators (hawks), and a couple to a dog attack. 3 weeks ago I bought 4 near-feathered keats... they went in the dog run along with two 2-month old turkey poults, and I was able to get the two remaining guineas herded in and captured, so they went in with the keats (they know the area now, so I was hoping they'd bond). the adult guineas weren't very interested in tolerating the keats for the first week, but by the second week everyone seemed to be getting along fine. after a week, we let the turkey poults out, but kept all the guineas in. once the keats finished feathering out (last wednesday) I let the lot of them out. we have free-ranging turkeys, chickens, ducks geese as well as the guineas. we round them all up and put them in at night, but they're ranging during the day. right now the keats aren't sure if they should follow the guinea adults or the turkeys, but they seem to opt for the guineas more each day.
for the first few days after turning them out, we kept feed out in the run and outside the run. starting today, we'll feed on turnout and before putting them up. starting monday, we'll feed only before putting them up.
I've seen our guineas cover perhaps an acre, maybe a little more - they are not covering a huge area, however, we haven't seen any ticks on people since the second week after we got them. we've only seen 3 or 4 ticks on the dogs and cats since end of july... prior to getting them at least one of the dogs or cats had a tick every other day.
I just hope they haven't eaten all my fireflies... I'd miss them.
so... how many do you need? not sure, ours aren't ranging that far. if you want more territory covered, you might need quite a bit more than we've got.
the one thing I *would* suggest is stay away from light colored birds (whites and lavenders) - everyone locally says they get picked off by hawks and owls first. we have pearls and royal purples.