Thought of a possible addon to help with this, You could code something to automatically ping when it sees a ping and it has a spell ready (I'm writing all this at work so I have no idea if it will actually work/has correct syntax).

Code:
PingReactor = AceLibrary("AceAddon-2.0"):new("AceEvent-2.0")

PingReactor.NeedzToPing = 0

function PingReactor:OnEnable()
  self:RegisterEvent("MINIMAP_PING")
end

function PingReactor:MINIMAP_PING(x, y)
  if self.NeedzToPing == 1 then
    Minimap:PingLocation(x, y)
    self.NeedzToPing = 0
  end
end

function PingReactor:GetReadyToPing()
  self.NeedzToPing = 1
end
Then on your main, the macro for the spell would be (If you want the spell centered on him):
Code:
/script Minimap:PingLocation(0,0)
and on the alts it'd be:
Code:
/cast INSERTSPELLHERE
/script PingReactor:GetReadyToPing()
The practical upshot is you should be able to hit both with one keypress and the lag will work FOR you instead of against you.