About security on Minecraft plugins

My son discovered MineCraft some months ago.
I decided to buy him a premium account.
He hosts a server to play with his friends.

Now, he wants to install kind of plugins to "hack" (in his term) his server to be able to dig larger part of land at once...

He told me that he would like to install the "bukkit" plugin
He told me also about a "server starter" "server starter" I'm less confident about installing this stuff...

Does exist a kind of "official" repository for these stuff ?
Which one I should not install for security reasons ?

The server is running on a window computer. I've read that exist an OS for running a server on Linux

Does exist a kind of "official" repository for these stuff ?

Google, really, easy to find official URLs for mods that result in the Minecraft or Bukkit forums.

For example, Minecraft TooManyItems yields Minecraft Forum - TooManyItems (306 pages).

Which one I should not install for security reasons ?

As long as you stay on (and read) trusted forums like the ones I mentioned above, nothing goes wrong. If your son does the same, and doesn't steer away from that, he knows what he is doing.

He told me also about a "server starter" I'm less confident about installing this stuff...

http://forums.bukkit.org/threads/winos-minecraft-delayed-server-starter-tame-your-restarts.11690/
explains "What is this", "Why would you need this", "How to Use", "Notes" and more...

The user that posted that has 1,700 messages and 40 likes, has been around for a year. Trustworthy.

The server starter you linked to is just batch files that point to specific installed instance of Java. Since you can have multiple versions of Java installed for a variety of reasons, those batch files seem to make an effort at controlling/clarifying which Java starts your server. You would be wise to learn the differences and control that yourself however.

The Bukkit server modification that lets you install plugins is safe, probably safer than the "Vanilla"/Mojang server itself even. Many people use it very successfully.

If you want to find plugins, you can look through Bukkit's own plugin list. As far as security on the plugins themselves though, that is definitely a concern. It's whatever the individual developer codes is what is run. There is no cross-checking/standards/filtering for safety with Bukkit plugins. Make sure you read through the plugin's thread on the Bukkit forums (the plugin list above links to the thread) and learn as much as possible about each one to be sure you are being safe.

Based on what you said your son wants to do, chances are you will want WorldEdit That is a very safe plugin itself.