There's a reason why the init scripts don't already exist. It's because not all flavors of Linux have the same requirements and setup for at-boot startup. You would need to consult the man-page for your particular flavor of Linux (usually init.d) for how to create your init scripts for the SHOUTcast tools.
There are also many DIY and How-To guides for generic daemon init scripts.
A cron job would kinda work but you also have to realize that just using a cron job to start the SHOUTcast tools would also be a waste of resources to have new instances being started every x minutes/seconds flooding your system with defunct processes. If you really want a quick and dirty solution to your daemon woes then you should take a look at my start/stop scripts I made a while back:
Even if you go with a proper daemon init script it would be a good idea to review the scripts I wrote to see how to generate a PID file so that the system can determine what to do when shutting down