There are a lot of quick get always from Kolkata are Puri a beach, ( personally the best waves in India), places in North Bengal and Sikkim ( I prefer Gangtok over Datjeliing and Kalimpong). I believe there are flights from Bagdogra to Karhmandu also. All these places have great resorts also. Kolkata is like most metro cities ( not really the traffic is much worse), I believe 2 to 3 days is more than enough.