If I can interject here - when it comes to 3D applications it is never a one time deal. Typically its an iterative process so you need to think about your pipeline and workflow efficiency.
As far as I know x3d is really re-packaged vrml. It seems quite limited right now as far as animation goes, although this may change in the near future. Also there are competing formats such as u3d used in Adobe Acrobat 3D, but this one is not open-source as far as I know.
If croquet can be incorporated in the current web 2.0, as you says, java applet style and remain 3D-interactive, then it sounds like you already have a web3d "hybrid-croquet" solution and you probably don't really need x3d.