When he was 18, Robert Kahn changed his name to Bob Kane. He said that it was around the time of the name change that he first began thinking of the character that would become Batman. His inspiration for Batman was one of Leonardo da Vinchi's drawings, the character "Zorro" as played by Douglas Fairbanks in the 1920 film "Mark of Zorro," and a silent movie called "The Bat."
Batman was introduced to the public in May 1939 in Detective Comics #27. By the next year Batman had a side-kick, Robin the Boy Wonder, and his own comic "Batman." Batman was so popular that DC Comics kept Batman in both "Detective Comics and "Batman." Both "Batman" and "Detective Comics" continue to this day. Detective Comics holds the title of the "longest continuously published comic book."
But as popular as the comics have been for the last seventy years, it is the 1960's campy TV series "Batman" and the blockbuster movies that has kept him "alive."
You own a nice collectible. There is a wide range of values for a Bob Kane drawing, depending on many variables. A simple drawing with a signature would probably be worth around $200. A more complex drawing with a signature would be worth as much as $1000.
Make notes regarding where and how you got the drawing from Kane's wife. Any pictures or supporting documents would add value to the drawing and make it easier to sell.