Several sensitive applications deployed within wireless networks require group communications. A high level of security is often required in such applications, like military or public security applications. The most suitable solution to ensure security in these services is the deployment of a group key management protocol, adapted to the characteristics of MANETs, especially to mobility of nodes. In this paper, we present the OMCT (Optimized Multicast Cluster Tree) algorithm for dynamic clustering of multicast group, that takes into account both nodes localization and mobility, and optimizes the energy and bandwidth consumptions. Then, we show how we integrate OMCT within our group key management protocol BALADE, in a sequential multi-source model. The integration of BALADE and OMCT allows an efficient and fast key distribution process, validated through simulations, by applying various models of mobility (individual mobility and group mobility). The impact of the mobility model on the performance and the behaviour of the group key management protocol BALADE coupled with OMCT, is also evaluated.