Remember, the ML-L3 is IR and needs to be line of sight, and then to every camera. That's not going to happen, and may not even happen for one camera if you're not close enough.
Realize with the Shutterboss II solution you're paying as much for the extra receiver as you are for the entire FreeWave Plus solution and you'll be left with only a single trigger. If you don't need the additional functionality of the trigger unit (i.e. intervalometer) you'll save yourself some money with the FreeWave units, and wind up with the ability to trigger multiple cameras independently as well.