Education is important for the primary applicant because all other visas are derivates so if you are married and with childrens,they dont bother about their work exp or education as a requirement to get the visa.
But if for example, one is married and the wife/husband has a degree and work exp, this will help your case to prove to the CO that you and your familly will not become public charge in US.
Individual forms for the familly members are to be signed by any member only if the member is an adult. For childrens underage, parents/primary applicant may sign the form.
The primary applicant have to sign also the primary applicantion form.