Hello,
every data source created determine the exact elements and extensions included in the sitemap, this is the base concept of JSitemap that allows integration with a lot of extensions.
To add K2 items to sitemap you need to use the wizard buttons to add data sources.
About the Joomshopping it's should be enough enabling the auto SEF alias mode to route the raw 'component/jshopping' to the menu alias used by Joomla. This is well explained in the component documentation and settings description.
best regards
John