You have 2 javascript errors on your page:
TypeError: ({pc:"100"}) is not a function
(function(i,s,o,g,r,a,m){i=r;i[r]=i[r]||function(){
www.cmstkids.org
(line 51)
ReferenceError: RokBoxSettings is not defined
...,">").replace(/"/g,'"');}});this.RokBox.Class=new Class({Implements:[Option...
I think that if you fix them the placeholder will show again. In the current version of CMC the placeholders are created with a js library, because at the time of creating the first version of the extension the html placeholder tag was not supported by all browsers. Now times have changed and this won't be an issue anymore with the next version.
Regards,
Daniel