Once you are PR, nobody cares who was the principal applicant anymore. Everybody's PR is equal.
If the husband is away but the wife and children live in Canada, she can apply for citizenship when she qualifies after living there for 3 years and then will apply for the children at the same time. Children do not have to live in Canada for 3 years to become citizens but they can not apply on their own. Parent has to apply for them and parent has to either be a citizen or a PR who is also applying for citizenship at the same time, see http://www.cic.gc.ca/english/citizenship/become-eligibility.asp#age
The husband can apply for citizenship later when he qualifies.