Kannur is a good option. It's got it's own airport which is connected well from Delhi, Mumbai, Pune, Bengalaru, Chennai... Else, you could take a train to Kozhikode and then bus it out too
Hey Gaurav! Kerala is a great destination for family vacations. However, to enjoy your trip thoroughly, make sure you plan for at least a week long stay. I'm adding an article link here that can help you plan your activities. https://www.tripoto.com/trip/kerala-tourist-places-luxury-holidays