Warming up to dogs

My kids have been deathly afraid of dogs since they were little. This has really made Mark sad and although he wants one of his own - he knows this won't be happening soon. He always tries to get the children to warm up to dogs, but they usually run and scream the second one comes anywhere near them. Recently Taylor has decided that some dogs are actually okay. This includes a total of three dogs and she will play with them for a considerable amount of time. This dog, Sadie, Taylor spent a lot of time playing with. By the end of the day we even convinced Dani to pick up the toy she brought and throw it for the dog. That seemed to be a miracle enough, but then even Sam decided that the dog must be alright and stopped screaming every time she came around. He would pet her as long as she wasn't running up to him and liked throwing the toys, although the dog would never bring it back to Sam since he only threw it 2 feet.