Best site on which to create a private social network?

[uknouluvme]

I'm looking to create a private social network for about 2000 children that are part of a global organization.
I came across different sites, etc. but I don't know how to compare them-
I want the one that's most user-friendly (similar to a Facebook interface), clean, ad-free, COMPLETELY private, economical, etc.
These are the ones I came across- if anyone knows more about these things and can tell me which one is best or suggest a better one I'd greatly appreciate it.
These are the ones I found:
socialgo.com
socialengine.com
phpfox.com
ning.com
wall.fm
spruz.com

[Martin Jess]

It’s a great idea that you choose to create a private social network, you can now create one for your own if you have the needed programming and web designing skills… You say that you’re creating the network for the children of a global organization. Getting expert assistance or choosing a company specialized in social network design is a good solution… They will guide you design and maintain the site in the right way. I shall suggest you to use this site.. http://www.fuchsiamac.com/ because the experts there helped me a lot in developing my social network site.