Absence from a board meeting does not release the director from responsibility for decisions made.
Conscientious performance is the standard.
It is your duty to review plans and policies and how they are carried out, not to be accommodating to people because they have been around for a long time in the organization and are doing their best. If a manager's actions are not in accordance with a policy, courts will usually assume the manager's acts to be the official stance of the organization and to have superseded the policies. Ensure that all employment and income taxes are paid. If you get directors and officers insurance, be sure the policy covers employee suits against the organization.