Well I have both. My keets haven't touched the ground yet though. I will take whatever precautions I need to, to insure my bees are as safe as possible. I might take the wait and see approach first though.
That being said, let me also say that the guineas are mine and so are the hives. Now if someone else's animal were attacking anything that was mine, I might feel different about it. Let me just say it would not continue.
All that being said, my animals are all contained. They can't go in anyone's yard. I wouldn't be able to keep them safe otherwise.
It is good that the bee keeper is openminded and willing to accept the guineas, although she has concerns......can you blame her? I would do whatever possible to keep her hives safe. Each of them are able to give her over 200 dollars a year in income, with no feed and very little maintance. Plus her hives are pollinating all your gardens and fruit trees probably in the whole town. Either keep the guineas in a fenced in yard or coop the bees. She might be willing to also take the wait and see approach, as I am, but you might consider that if her colonies are irradicated, ya'll really owe her something and its not going to be cheap. Still she might be a quiet person and not want to make a stink about it, even if she does suffer losses. I am all for your dad having the guineas, but the neighbor needs to be considered too. Her equipment was very expensive, plus she had to put them together and start catching swarms and probably received more stings than every member in your family combined.