The 17-year-olds were arrested in November for calling Ameobi a "nigger" on the social networking site.
It was understood one youth made the initial comment and his friend followed it up with a supportive tweet which also had a racial element.
The decision not to prosecute the pair was taken after consultation with Ameobi - the younger brother of fellow Newcastle striker Shola - and the football club.
Both youths have admitted their involvement and accepted final warnings at a Northumbria Police youth surgery on Monday.