I'm not sure if Christmas would be the right time to be in Croatia. But since you'll be in Zagreb most of the time, it won't make much difference.
Why do you choose January? Spring and Summer is the time when people visit Croatia.
2 days zagreb the rest (5 days) in the island.
Long Story short. I have to serve in the bloody army after I graduate (Mandatory). Last chance to travel in the next 2 years.
GF flying in after Christmas.. spending 1 week in Cairo and another week somewhere else that is weird. Malaysia has the same weather all year.... I read Croatia is cold.
Malaysia better option no?