When I have gone out with my young child to local restaurants, I have found several things that have worked for me in terms of keeping my child calm, relaxed and bordom-free so I can actually enjoy the meal out too.  Hopefully some of these ideas could work for you:

1.) Bring some play-dough with you with some small tools for playing with it.  I know many parents cringe at the idea of playdough, but this really works.  It keeps the children engaged for long periods of time and can even be fun for the adults to, if you let it.  Also, you don't have to worry about the mess on your own floor and the children get some "play-dough" time.

2.) Bring a small baggie of crayons and some paper or coloring sheets with some of your child's favorite characters on them.  Don't always assume the restaurant will have this kind of thing.

3.) Teach a fun game to your child like "Rock, Scissors, Paper" or "Riddly, Riddley, Riddley, Ree."  Your child will love to play the game, you can teach while you are waiting for your food, and you and your child will both benefit from the interaction.

4.) Go to buffets whenever possible.  This cuts down on your wait time for your meal which is when most children tend to get harder to handle.

Hope these tips help!