Yes, guineas can fly to safety and they are VERY loud when they warn the other guineas about a predator. Providing you have trees for them to fly up to. Silkies don't fly or even roost, so are easy pickings for predators.
The guineas behavior might insite the hunting or chasing instinct in your dogs more than the silkies did. I have several rat terriers and they did chase the guineas and didn't bother my other chickens. Most times the guineas were able to fly away from them. One did get trapped along the fence and the dogs were plucking the poor thing alive. I chased them off and the bird was ok.
I sold the guineas after that, mainly because they were so loud.
Carrie