Medal of Honor: Heroes 2 on Wii does not support multiplayer of any kind. It is a strictly single-player campaign experience.
Medal of Honor: Heroes (2006) (the first PSP port on Wii) features 4-player split-screen multiplayer. It lacks online, but offers local versus modes (Deathmatch, Team Deathmatch, Infiltration) on several maps.
If you want online military shooters on Wii, options are extremely limited: Call of Duty: Modern Warfare Reflex, World at War, Black Ops, Conduit 2, GoldenEye 007 (WFC shut down 2014; private servers like Wiimmfi restore online for some).