See the link at the end for the complete IRS FAQ on which ITIN expire and how and when to renew.
IRS has annouced that ITIN’s that will expire on December 31, 2017, are ITIN’s that:
-were not used on an income tax return filed for 2014, or 2015 or 2016, or,
-whose middle two numbers are 70, 71, 72, or 80
If an expiring ITIN will be used on a tax return you will file for 2017, IRS advises you to begin the renewal process “immediately” and not wait for the CP-48 notice that you will be mailed over the summer. IRS estimates 7 weeks as the time it would take to process an ITIN renewal request.
If an ITIN for one person shown on a tax return will expire, then all individuals shown on that tax return may apply for a renewal. Yes, it could be a good idea to get everyone on the same cycle.
Original official documents are required to support the W-7 renewal application. Ideally, the applicants can work with an IRS authorized Certifying Acceptance Agent (CAA) or visit a designated IRS Taxpayer Assistance Center (TAC) so that they will not need to mail important documents with their application.
The Form W-7 must be the version with the revision number 9-16, not an older version of the form.
https://www.irs.gov/individuals/itin-expiration-faqs
https://www.irs.gov/individuals/acceptance-agent-program
https://www.irs.gov/uac/tac-locations-where-in-person-document-verification-is-provided