A native of Kerala here. You are most welcome to my state. You might find more topics for your documentary here, for ex: The religious harmony of Kerala, while the other Indian states are still divided on castecism. The high HDI and literacy (almost 95%) of Kerala. Here is Kerala Government's tourism website for more information to plan your visit.

https://www.keralatourism.org

You can get Visa on Arrival too https://www.keralatourism.org/visa-requirement.php

If you find it hard to DIY. You can contact professional tour operators in Kerala to plan your vacation.

PS: Kerala has very high literacy about 94.59. Most of Keralites can write/read/speak English. All the information signs/shops/hotels are in English & Malayalam. You will have no problem finding your way around and asking for directions even without a tour guide.