HgCl2 and NaCN have similar acute toxicities, but I am much less fearful of NaCN than HgCl2. Mercury is a cumulative poison, whereas cyanides exhibit relatively little cumulative toxicity. This is not to say that there are no chronic effects from cyanide exposure - there are! - but that repeated exposure to small quantities of mercuric chloride is far more likely to harm your health than repeated exposure to small (emphasis on small!) quantities of cyanides.
Do not inhale or make skin contact with solid cyanide salts or their solutions. Aqueous cyanide solutions slowly release HCN, and release it much more rapidly when acidified; this is also strongly affected by temperature.
Put most of your safety efforts toward prevention of accidents, not treatment. I assume you are working solo. You won't have time to administer any treatments to yourself if you are poisoned by inhalation, so make sure you aren't exposed in the first place.
Cyanates undergo hydrolysis to ammonia and carbon dioxide, and aren't especially toxic even if discharged as such. A variety of cyanide/cyanate treatment reactions are described here, using environmentally friendly peroxy compounds: http://www.h2o2.com/applications/industrialwastewater/cyanide.html (http://www.h2o2.com/applications/industrialwastewater/cyanide.html)