Ideal is to book for your first day and then decide further after reaching there. Most of the Hotels in Kochi, Trivandrum and other cities of Kerala have short packages for 1 N, 2 N and more that can be booked with complete control and flexibility and booking after reaching there saves a lot than booking over phone or mail or any other media. If you are first timer and not able to manage then just go with booking accommodations for initial phase of journey.