As long as you follow the appropriate precautions, using dichromate is safe. If mixing from powder, handle it in a well ventilated area and wear gloves and a dust mask. Once dissolved in solution it becomes much easier to handle (no risk of inhalation), but you're obviously not going to want to make skin contact with it (so once again, wear gloves). The dichromate will disappear from the carbon print after it is washed, and a solution of sodium bisulfite (IIRC) will clear any remaining amount (at which point the print will be perfectly safe to handle with bare hands).