I had the same desire to remove the published date. In my case I wanted to remove them from ALL pages.
One way to to do this is to adjust the Placement of Shapes...
The Shape you need to influence the placement of is the Parts_Common_Metadata shape. To make it invisible you make the placement value equal to 'Nowhere'.
So I added this to a placement.info file inside my theme folder:
<Match DisplayType="Detail">
<Place Parts_Common_Body="Content:before"
Parts_Tags_ShowTags="Content:after"
Parts_Comments="Footer"
Parts_Common_Metadata="Nowhere"/>
</Match>
<Match DisplayType="Summary">
<Place Parts_Common_Body_Summary="Content"
Parts_Comments_Count="Nowhere"
Parts_Tags_ShowTags="Nowhere"
Parts_Common_Metadata_Summary="Nowhere"
Fields_Common_Text="Nowhere"/>
</Match>
If you want this to apply only to certain content types you can wrap the above within a parent tag such as:
<Match ContentType="Blog"></Match>
I'm not sure how you would apply this only to the Welcome page though...