If you need the AI to go to an exact spot, then a waypoint is no good: waypoints are completed when the group gets to within a certain distance. What I suggest is a waypoint at the exact spot, to get the group close, then runa script from the waypoint
; script to make the loon move to the right spot
#lop
leader grp1 doMove getPos GP_1
~2
? GL_1 distance leader grp1 < 2: goto "end"
goto "lop"
#end
; insert the consequences here
exit
Syntax not guaranteed but the idea is that as soon as the WP is completed the group leader (don't use a named loon in case he has been killed) will go to the right place and when he gets there the consequences occur.