Circles with children expansion

[ant...@appstract.dk]

I have been trying a simple example, which no longer seems quite simple with box2dweb.js and raphael.js,

Which is as follows:

I have a tree data structure, where a parent node has multiple children, all I want to do is represent them as circles. 

That would mean that each time I click a circle it pops out its children (if it has any), and has a springy edge from the parent.

I have been able to do this with Box2dWeb, but its gets quite messy, as circles get trapped in between edges of other circles from different levels etc. 

Any suggestions as to what kinda Joints, should i use so that (a child, its parent and its edge) dont entangle with others??