It is too risky. I would not and donot let the rabbit be with the guinea pigs. Some rabbit, asfar as I understand, can carry pasteurella or bordatella withoutshowing outward symptoms. The guinea pigs could get this andbecome very sick quickly.
Also, the rabbit could easily hurt the pigs. I have a rabbitand two pigs and it is really tempting to let them play together and itmight be very cute. However, if something were to happen, I'dnever forgive myself and I dont want to live with that.
Hope this helps