I suppose you try to use some very old version (earlear as jQuery UI 1.8) of jQuery UI. The name of $.Widget was changed in jQuery UI 1.8 to $.widget. See the old post about the subject. Try to use more recent version of jQuery UI.
All checkboxs are set per default. Why you don't stay by defaults? If you develop intranet application then increasing of file size is not real problem. If you develop internet application or if you develop applikation for clients which have always access to the internen you can don't download any jQuery UI at all and use jQuery UI from one well known CDN. In the case your application will have better performance.