CiviCRM, Ubercart, and donations through the shopping cart
we have found that using CiviEntities opens the door for using Rules directly to control what gets pushed in to CiviCRM and how (in our case with Commerce not Ubercart). I can't really flesh out more on this as Eileen did the work  and she is probably en route back from the Sprint in Denver. Perhaps the above is enough to give you something to look in to if no one else comes back with a more succinct solution.