If you have a large enough container you may be able to trap the poor piggies and at least get them inside and safe until you can contact the owner again.
Take a large container and make some holes at the bottom (so that it won't flood if the rain starts up again) and line it with a towel or similar, something nice and cozy. Put some food (they seemed to like the carrots before, try that) in the bottom and then make a "ladder" leading up into the container. Put the whole lot on your yard as close to where the piggies are known to hang out as you can, and check on it every so often.
The idea is that they will climb up the ladder to get to the food, fall into the container and not be able to get back out, a sort of pit trap really. The same thing will work on a smaller scale with other escaped animals, e.g. hamsters. (Which is how i learned it, lol)
After that, personally I would bring them inside, make sure they were healthy and go speak with the occupier/owner of the place, ask if they still wanted the guineas and if not, take them on as you've already said you're interested in doing that.
If you're not comfortable with trapping them maybe you could make them a little shelter, a cardboard box on a couple of bricks with some shredded paper, a water bowl and maybe some food inside. Stick a tarp or cut open plastic sack over the top to keep off the rain. At least they'll be comfy.
If you don't catch them, i'd call the spca. They are in danger and need helping, evidently their owners aren't caring for them as they should be.