There is currently no New Zealand standards regarding bathing in water which has a boil water advisory, however the Australian standards state:
Under most circumstances it is not necessary to boil water used for other household purposes. As a guide, if water has less than 200 E. coli (or <200 enterococci if sea water) per 100 mL it should be safe for showering and bathing for all except the very young, who can swallow more bath or shower water than older children and adults. As a precaution toddlers and infants should be sponge bathed. Do not gargle contaminated shower water.
Washing of dishes by machine or hand is acceptable, provided dishes are air-dried. No additional precautions are required for washing clothes.