arherp - haha, yes, I would be safe from ticks inside the guinea tractor! Unfortunately I would not be safe from their shrieking, so it kind of evens out...
The two biggest problems are: a beehive (which we didn't have when we got the guinea keets last summer), and a dog that refuses to go to the bathroom on the leash and may or may not have killed a guinea earlier this week while he was loose.
I could explain the whole chain of events, which might make me look like less of an idiot, but that's the gist of it.
We also live fairly close to a busy road, and it sounds like guineas are more prone to wandering than chickens are. Basically, I'm worried that when I phase the guineas into free-ranging, they'll a) eat all the bees, b) get killed by the dog, c) get killed by cars, d) continue to annoy me and not make a dent in the tick population, or e) some combination thereof.
For the first time we have chickens that free-range during the day, so maybe they'll take care of some of the ticks.