Platform based computing modules such as embedded systems and micro-servers are multichip systems with in-package memory and processing chips. These computation expensive and memory intensive multichip systems need an energy efficient broadcast/multicast capable interconnection infrastructure to support the cache coherence protocols and system-level synchronization mechanisms. State-of-the-art interconnections do not provide an efficient support for broadcast/multicast communication. Consequently, a small proportion of such one-to-many traffic, increases the energy consumption and message latency while decreasing the data bandwidth for chip-to-chip communication. To address this issue, we propose the design of a one-to-many traffic-aware Wireless Network-in-Package (WiNiP) architecture. Using a one-to-many traffic-aware Medium Access Control (MAC), the proposed WiNiP architecture reduces the message latency of such traffic for both homogenous and heterogeneous multichip systems with in-package memory. We demonstrate with cycle-accurate simulations that the proposed WiNiP architecture reduces the energy consumption and latency while increasing the bandwidth by up to 54.7^% for multichip data transfer compared to state-of-the-art wired NiPs.