I think
sadbhawana = Goodwill
Bhawana = emotional or moral sensitivity esp in relation to one's principle or dignity.
Biwekta = it's like ability to differentiate right or wrong, smart intelligent ability or wisdom/knowledge

Sadbhawana party could be ' Goodwill Party'. 
'The party of sympathy' makes no sense, esp when we translate Nepalese verses to English , we usually get hilarious meanings.
It's because most of every single word in english tend to carry many different meanings based on various situations and the way it's used.

I don't have nepalese to english dictionary but based on my knowledge, I'm telling you this :D

I'd like to know more as well, if there is any other definition more than that.