Using crontab is the way to go. There isn't anything deep voodoo about cron. The crontab information is indeed stored in a file, but that doesn't mean adding something to the file is going to work. On many OSses, nothing will happen. You would usually have to use the crontab command, either interactively (using an editor), or by passing it a complete file. The crontab command checks the file for syntax errors, and then tells the cron daemon there's a new configuration file.

You can automate that process, but details of how to do that differ between OSses. Personally, I think setup scripts that modify configuration information (like crontab entries) are a big no-no. If people cannot figure how to add a line (you can give them the line they need to add) to their crontab, they shouldn't run automated processes.

Abigail