Hi
1, The only drawback applying as a family, is where one family member is ineligible or CIC decides that a RQ is in order. Then the rest of the family has to wait until CIC determines that all family members are eligible
This isn't always true, if for some reason ( missed test, RQ or others ) IRCC will proceed with the other family member's applications and won't wait for the one having RQ or missed the test or has to go through hearing to process the rest of the family.
https://www.cic.gc.ca/english/helpcentre/answer.asp?qnum=734&top=5
If we receive the necessary information and documents, applicants 18 to 54 years of age when they signed their application will be invited to write the citizenship test.
After the test, you or a family member may be asked to:
re-write the written test; or
attend a hearing with a citizenship officer or a citizenship judge
If this happens, we may process the other family members’ applications separately. This process might mean that they will attend an earlier citizenship ceremony and become citizens faster than the one re-writing the test or attending the interview.
We will tell you before we process your family’s applications separately. We will also send you a form that you can use to ask us to process the applications together. If you want the applications processed together, we will pause the other family members’ applications until after the second test or interview.