You need :
- Valid passport (valid 6 months after the date of return)
Minors must also have an individual passport.
- Visa is required. Please check on India embassy how to get your visa.
For many countries, you can use a e-visa. Easy and practical : https://indianvisaonline.gov.in/visa/tvoa.html
(application form; registration of an identity photo to Indian standards – colour, JPEG format; payment: 80 US dollars); once the e-Tourist Visa has been received by email (3 to 4 days), print it and present it at the airport of arrival in India.