Hello, unfortunately, no matter how social a particular animal may be, you should never allow cross-species contact. In fact, when it comes to hamsters in general, you may not even want to allow same species contact! Guinea pigs and hamsters would never come across one another in the wild, and hamsters are naturally solitary so they wouldn't get anything out of being introduced to your guinea pigs. It would be best just to play with your hamster yourself, and let your guinea pigs spend time with one another
I'm not super experienced with guinea pigs, so someone on here who is may advise you better and in more detail, but guinea pigs should never be kept alone. Guinea pigs kept by themselves develop neurological problems which ultimately lead to a premature death after a life of suffering. Worry not as having two guinea pigs is really no more work than having just one, plus two is always much more fun! If you cannot get a pair of guinea pigs, I'd recommend holding off on getting them. Best wishes
