Scruffy

I would like to run a big dig server for a few friends and I. However, my friends would rather have vanilla minecraft spawn rates for ores. Is there a way to lower the rates and make ores spawn in their natural levers without breaking the whole pack? Also, if anyone knows how to start/run/maintain a big dig server and are willing to give me a few tips and help, that would be appreciated. (I have never run a minecraft server but am willing to learn how to)