Situational Awareness (SA) dissemination in tactical mobile ad hoc networks (MANETs) plays an essential role in command and control systems for military operations. This task is particularly difficult in highly dynamic and complex environments with strict resource constraints on mobile units. In this work we present a design of SA dissemination schemes based on the multipoint relay (MPR) technique. We implement the schemes on a simulation platform and investigate their effectiveness in a real-time manner using novel metrics focusing on the completeness and freshness of SA, as well as the network traffic overhead and local processing cost. Two mobile scenarios, including one that is based on the Reference Point Group Mobility model, are set up to simulate the real-world behavior of tactical MANETs. The MPR-based methods are compared against an alternative scheme, Opportunistic Situational Awareness Passing, where the simulations highlight tradeoffs and provide insight into selection of design parameters.