Yes, typically VISA is required. The requirements vary by country but mostly it is an E-visa and takes about a week for the 30 day tourist Visa. American passport holders planning a visit to India for tourism require an E-VISA and must be acquired prior to entry. It is done online and typically takes a week
Wedding and its associated events are just 2 days - Friday (5/15) and Saturday (5/16). Considering it is a long flight to India we would suggest atleast a week long trip. Different parts of India are incredibly diverse in culture, language, food, geography and tradition. Think of different states in India similar to different countries in Europe, but hoping a week would give you a flavor/idea of what India has to offer and convince you to be back to explore a different region in the future.
Taj Mahal is a day trip from Delhi ( North India). There are plenty of Tour operators for this route. If you would like to visit Taj Mahal, the best plan would be to enter or depart India from Delhi (IGI) . Delhi is very well connected to the US/Europe and has multiple domestic direct flights to Cochin (COK). Land in Delhi, explore Delhi for a day or 2, visit Taj Mahal and then head to Cochin or other way around. Summer in Delhi is very Hot and Dry ( Hello Dallas !) in May - ~95/75 F
All major cities have airports - Indigo and Air India are most popular. India has Uber and Ola ( its local competitor). Most hotels would have their own Cab partners too. Google Maps works well. Delhi and Cochin have good metro connectivity and Tuk tuk and local buses and trains are available for the adventurous ones. Would recommend sticking to Uber or hotel cabs ( they are much cheaper than in US)
Mid May is tail end of summer in India so generally pretty hot. Delhi is inland and would likely be 95+/75 with low Humidity Kochi is off the coast and has tropical monsoon climate and would likely be 90/75 with relatively high humidity during the day
Typically Kerala Christian weddings people wear South Indian/Kerala Traditional or dressy casuals/Sunday best. South Indian Traditional Men : Kurtha + Mundhu/Pant Women : Saree or Salwar Kameez/Churidar If you want traditional Indian, you should find them in Indian clothing stores in Houston but we would suggest coming to India and getting them from stores like https://www.fabindia.com/ All events will be indoors but Cochin is likely to be hot and humid, so dress comfortably. If you want suggestions, we can provide more details
India has 22 officially recognized languages. Hindi is widely spoken in Delhi and Malayalam in Kerala. But in most major city centers English is commonly understood
1 USD = 90 INR (Indian Rupee) Most of India works on Digital payments ( QR Codes) but most decent size establishments would take credit cards ( Visa/Mastercard; Amex is not always accepted). I would recommend confirming international credit card is accepted before you make a purchase. Carrying Cash ( ATMs are available everywhere) with you is advisable.