Take a chance & go for it.
I am invited to a surprise dinner party of a friend of mine and I don't know if should go since I don't know anybody there, and I only met the host once and we barely talked... Should I go? I'm kinda shy, that's what keeps me back.
Going to these parties is one way to overcome your shyness. You don't have to be the life of the party and meet everyone so just go and find a few you would like to meet and go for it. Chances are there will be some others that are shy too and may approach you so nothing gained if you don't at least try here and who knows it may even change your whole world for the better and that's a good thing here. If you do go, please let me know how it turned out as I'm interested and may be able to help you overcome your shyness so please let me know. Go, have fun, and Merry Christmas