Does normal blood sugar vary by age? What are the normal fasting and normal after-eating blood sugar ranges?

Same. Except for newborns, normal fasting blood sugars range from 65-99 mg/dl. 2 hours after eating blood sugar should be no higher than 139 mg/dl to be considered in the normal range.
No; 100; 140. Normals are the same regardless of age. Fasting under 100 (110 according to others); 2 hours post meal under 140.