Trigger over the door area:-
Activation box: Anybody present Repeatedly
On activation: thislist select 0 setPos [(getPos object nnnn select 0) + x, (getPos object nnnn select 1) + y, h]
Alternatively, if you want the whole group to be teleported:-
On activation: "_x setPos [(getPos object nnnn select 0) + x, (getPos object nnnn select 1) + y, h]" forEach units group thislist select 0
Syntax not guaranteed.
That will teleport the first loon to enter the trigger. If two enter simultaneously then only the first will be teleported. Set the trigger area to make sure this doesn't happen. Maybe place some furniture near the door as well, to make sure loons can approach only one at a time.
The trigger will teleport as many people as you like, one at a time, as long as they don't enter the trigger are too fast.
Is that what you want?