Corrected entry: Maya is 10 years old. The actions of the movie stretch from 1992 to about 2003. (Will's birthday party takes place before 2000 because Clinton is still in office). Will professes his love for April at that time, finds the copy of Jane Eyre shortly thereafter, and waits 3 years before giving it to her. Therefore Maya was born about 1993, but Will and Emily were not together then.
Corrected entry: William and April are debating which cigarettes are better to smoke, American Eagles or Marlboro Reds. They go outside to see which cigarette will last longer if they smoke them at the same time with the same drag length. In the scene, William buys a pack of Marlboro Reds. The filters on those are a tan/brownish color. When he is outside with April smoking, the color of the filter on his cigarette is white, which is the filter color of a Marlboro Light.