Providing normal users(non-root) with initialization and shutdown auto-run capabilities

I'm hosting an experimental/testing Linux box, running Debian Wheezy 7.4.0 distribution. Different users log into the machine over ssh to their accounts and are allowed to run the development tools and leave their programs running as services in background if they so wish.

Since this is a testing machine for all kinds of purposes there is often a need to restart the whole machine and then the users have to log back in and restart their user-space stuff that was running. I would like to automate that. Basically I would like to provide the users with a mean to launch stuff right after the machine boots up(after everything else is initialized) and a mean to launch stuff upon system shutdown(with no time limitations, basically stalling the shutdown until all those shutdown user processes have completed).

What I have tried so far:
I've created an init bash script, by following the principles found in the 'skeleton' template file under /etc/init.d/ (Skeleton template source code: https://gist.github.com/ivankovacevic/9917139)

My code is here: https://github.com/ivankovacevic/userspaceServices

Basically the script goes through users home directories and looks for executable files in corresponding subdirectories named .startUp, .shutDown or .status. Depending on the event that is currently going on the scripts get executed with su as if the users have started them themselves.

The problem I'm currently facing with this approach is that there is a strange process left hanging after the system boots and the script starts all the processes of other users. This is how it looks in the processes list:

UID        PID  PPID  C    SZ   RSS PSR STIME TTY          TIME CMD
root      3053     1  0  1024   620   1 17:42 ?        00:00:00 startpar -f -- userspaceServices

I don't know what that process is and man page for it does not mention the -f argument. So I'm clueless but I must be doing something wrong since no other script/service from init.d leaves such a process hanging after boot.

So I'm looking for someone to help me debug this solution I have(which also seems a bit complex in my opinion). Or give me some idea how this could be implemented in an entirely different way.

UPDATE
I've started a separate question for the startpar issue: startpar process left hanging when starting processes from rc.local or init.d

UPDATE 2
Problem solved for my original solution. Check the previously mentioned question for startpar. The code on GitHub is also corrected to reflect that.

UPDATE 3 - How to use crontab
As Jenny suggested, regular users can schedule tasks to be executed once upon boot using crontab. I find that to be the easiest method, if all you need is starting user tasks on boot and not shutdown. However there is a drawback that users can leave cron process "hanging" as parent when they launch on-going, service-like tasks. First let me just explain how it works:

regular users themselves should call:

crontab -e

( -e as in edit ) Which opens a default console text editor with their user crontab file. To add a task to be executed at boot, a user must add one line at the end of the file:

@reboot /path/to/the/executable/file

Now if the user would do just that and if that file is not just some simple script that linearly completes something and ends, but some sort of watchdog for example, after a reboot you would end with something like this in your processes list:

    1  2661 root       20   0 20380   860   660 S  0.0  0.0  0:00.00 ├─ /usr/sbin/cron
 2661  2701 root       20   0 33072  1152   868 S  0.0  0.0  0:00.00 │  └─ /USR/SBIN/CRON
 2701  2944 someuser   20   0  4180   580   484 S  0.0  0.0  0:00.00 │     └─ /bin/sh -c ./watchdog
 2944  2945 someuser   20   0 10752  1204  1016 S  0.0  0.0  0:00.00 │        └─ /bin/bash ./watchdog
 2945  2946 someuser   20   0 23696  4460  2064 S  0.0  0.1  0:00.01 │           └─ /usr/bin/python ./some_program.py

To avoid that the user needs to modify his crontab entry to look like this:

@reboot /path/to/the/executable/file >/dev/null 2>&1 &

The redirections of file descriptors are optional but recommended to keep it clean. If you want to study why, try looking at them:

ls -l /proc/pid_of_started_process/fd