First let the dog sniff the guniea pigs but make sure the guinea pigs are in their cage, if yoru dog shows no sign of aggresion, discomfort bring the guniea pigs out of their cage, hold them in your hands and again let the dog sniff them. Again if your dog reacts calmly place the guniea pigs on the floor ( in a closed area like the dining room) and let them play or do whatever they doo! If your dog gets angry or you know becomes aggresive take the guniea away and in a firm voice tell the dog NO! Hope i helped! GOODLUCK!