Move sub sites in to separate site collections SharePoint 2010

Hi,

Recently one of our customers wants to move their SharePoint 2010 Sub sites in to a separate site collections.

This is a migrated environment from SharePoint 2007. All the sub sites (around 250 sites) are created under one site collection (one content data base).

My basic requirement is if I want to move most of the sub sites in to separate site collections with separate content data bases.

(Most of the Sub sites contain child sites. In that case we are going to move that parent site to separate site collection)

What will be the best possible way to do it?

Thanks in advance

Tharindu