I have 6+ year old kids and I know how difficult it is to make them sit for more than an hour (movie theater is an exception of course :)). It is always fun to travel with family and a challange to keep kids engaged. I have been using card games to keep them busy and have found them quite effective. Below is my pick
A board game for kids above 8, it is a classic game of buying and selling. Players buy , sell or trade properties. Aim is to drive the oppnonent to bankruptcy so that you have a monopoly over the economy of the city. The game originated in America around 1903 has become one of the most popular board games across the world. Very affordable and is available on various retail sites for around Rs 400 and more.
UNO Card game
A popular card game suitable for 7+ year olds. It is a popular family card game. Rules are easy to understand and kids pick it up quite easily. One the cards are distributed the aim of each player is to get rid of his/her card before other players do. The player who wins the game gets the point according to number and type of cards left in opponents hand. There are lot of vedios on internet for you to start learning.
Suitable for kids 7 year and above. It is basically a naval strategy game. Need 2 players. The objective of the game is to destroy opponents fleets. Not very costly and available on almost all retails sites. Check it out.
Ludo / Snake and Ladder
These are the most popular board games which we all have grown with. We have new and new games being launched but these still remain as popular as they were.