Final answer:
In the scenario given, the NIMS Management Characteristic being supported is Accountability, as it ensures a clear record of actions and adherence to the chain of command.
Step-by-step explanation:
The NIMS Management Characteristic that is being supported in the scenario is Accountability. As a Disaster Program Specialist in charge of teams trained to help in sheltering displaced persons, checking in before beginning the task reinforces the NIMS principle of accountability. This involves keeping track of personnel and resources, ensuring that the chain of command is adhered to, and that there is a clear record of actions and decisions made. Accountability is crucial in emergency management to maintain effective operations and ensure the safety of both volunteers and those being assisted.