There are also the same kind of fan but 120V, so if you dont want to mess with power supply, if you dont have an engineering background, it is going to be better to deal with this kind of fans.
About the number of fans, it sounds good, but I cant certainly tell you that is going to be enough, it will depend the circulation is creates within and outside the kegbox and your local weather. If you can get it cool enough, you just need to increase heat transfer and it mean better flow (More fans)