By now, hip-hop has become a mainstream part of the cultural landscape for children on shows like ''Sesame Street,'' ''Yo Gabba Gabba!'' on Nickelodeon and ''Choo-Choo Soul'' and ''Handy Manny'' on the Disney Channel. But when Rona Brinlee, a bookseller in Atlantic Beach, Fla., first heard about ''Hip Hop Speaks to Children,'' an illustrated anthology of poems and song lyrics, she worried that prospective buyers might shy away. With previous volumes of poetry for children, she had noticed that the books were popular among grandparents looking for gifts. ''I didn't know if these same loving grandparents were going to say, 'Wow, hip-hop,' '' said Ms. Brinlee, who owns the BookMark, an independent bookstore. ''Because some are going to make assumptions that this is violent, or they just don't know anything about it.'' [ABSTRACT FROM PUBLISHER]