The problem is to have a smooth automatic shutdown. This means killing daemons normally, and unmounting devices. If you use the lock init children features, you must allow a process to kill them anyway. If a daemon is not killed, it could busy a device which would not be unmounted, and which could be trashed. So the two facts are importants.
So we must find a program which is executed only for shutdowns and which kill daemons or unmount devices. Unfortunately, this program does not exists. (It will at least call unmount). Fortunately, LIDS give you the possibility to make the kill license inheritable, that is to say that the mount would be authorized to unmount devices only when it is called by this program. Idem for killing daemons.
This program is either /sbin/shutdown when called with the -n option, which is deprecated, or more probably the script which execute each init script in runlevels (/etc/init.d/rc on Debian). It is the one which will call init scripts for stoping all daemons and unmounting devices.
You can modify it to switch only to runlevel 2 and 6.
See 6.1.14 and 6.1.16.