You need to add to web-client-config-custom.xml in alfresco/extension
<config evaluator="string-compare" condition="Action Wizards"
replace="true">
<subtypes>
<type name="my:content" />
</subtypes>
<specialise-types>
<type name="my:content" />
</specialise-types>
</config>
And then the trick is to provide title & description for the types in the content model or via messages/properties; otherwise they will not be there.
Wrote about similar issues here: http://experiencewithalfresco.blogspot.dk/2012/08/remember-to-define-title-and.html