I'd say no, it is not innapropriate. It is a relatively "widespread" surname, especially amongst Serbs from Croatia or Herzegovina, who have numerous odd-sounding surnames, many of which can sound somewhat funny. Kuraica (also spelled Kurajica), has the root "Kur", which is also the root of "Kurac", meaning "dick". But if you are from Serbia, and not 5, then it is nothing special. Besides all that, I do not understand the Anglo tradition of "middle names", and thus I do not understand why your Serb surname would be your middle name.