You cannot file an extension of status. In order to file an extension of status, the applicant must intend to leave the United States. Your parents have no intention to leave the United States.
In addition, it may not be advisable for your parents to file for adjustment of status. Your parents may be found to have immigrant intent. This can lead to a permanent bar to admission. Whether this will be an issue will depend upon their intentions at the time of entry. If your parents adjustment applications are denied, it is unlikely they will be allowed to enter again with their tourist visas.
you can read more about adjustment of status at http://myattorneyusa.com/adjustment-of-immigration-status.
Answered on May 26th, 2016 at 2:11 PM