In next-generation passive optical networks (PONs), the traffic exchanged among optical network units (ONUs) belonging to the same PON, i.e. inter-ONU traffic, will increase because of emerging applications and services such as the smart grid. Applying network coding (NC) techniques to the inter-ONU traffic will improve throughput, security and reliability. However, the implementation of NC causes additional queuing delay at the optical line terminal (OLT), and degrades the fairness among coded and uncoded inter-ONU flows in terms of latency. This paper proposes a novel bandwidth scheduling technique, i.e. a grouped random scheduling (GRS) algorithm, to reduce the additional queuing delay at the OLT. In addition, a priority index (PI) is defined to further reduce the latency of coded inter-ONU flows, and an adaptive priority scheduling (APS) algorithm is proposed to improve latency fairness among coded and uncoded inter-ONU flows. The proposed techniques are validated by numerical analyses and simulations.