Four would be better. Greyhounds should not be left unattended in a yard, particularly if the fence is six feet or less. They are incredible jumpers. Greyhounds have half the body fat of other dogs and hence are more sensitive to the cold. Greyhounds and kids .
Most greyhounds are very tolerant of small children.
As with any dog, play should be supervised and the child should not be permitted to abuse the dog. Normally a greyhound that is being abused will walk away. In rare instances they have been known to snap at the child. Greyhounds and cats . Most greyhounds are fine with cats.