More and more Quality of Service (QoS) sensitive applications, such as streaming media, high bandwidth content distribution and VoIP, will be deployed in Mobile Ad hoc Networks (MANETs) as part of the pervasive computing realization. However, traditional QoS guarantee technologies cannot be used directly in MANETs due to the dynamic network environment. This paper proposes a QoS management mechanism combining Caching and Backup Service Paths (CBSP) and an Enhanced CBSP (ECBSP) for soft QoS guarantee in MANETs. In CBSP, Service Provider Nodes (SPNs) with distinct Service Paths (SPs) providing the required service are found in the MANET during the service discovery phase. The client node then selects one SP to get the service and the other SPs as Backup Service Paths (BSPs). If the serving SP fails to serve the client node, the client node can handover quickly to a BSP and consume the resource in its cache during the handover operation in order to avoid service interruption. In ECBSP, the required data are further divided into several segments and transmitted concurrently to the client node through different SPs for enhanced availability. Simulation experiments in ns2 show that CBSP/ECBSP can improve the performance of applications in MANETs effectively.