The names of the three ships are not the most important fact about Christopher Columbus, but I think it is important to start teaching the truth about Christopher Columbus. He was not the first person who found the Americas. He was also not a good person and was responsible for the enslavement and death of native people.
I would argue that the names of the three ships are not truly important to the story of what happened. Kids really just need to know what Columbus was trying to achieve and what he helped to discover. When kids get older, they truly need to know the horrible things that he did.
The names of the three ships are not the most important fact about Christopher Columbus for kids. The most pertinent facts are that his men suffered greatly in the voyage and that he discovered America. The names of the ships are important in that they are remembered and that they reflect the Spanish-sponsored voyage to the New World.
The names of the ships are important to teach kids because they fit nicely into song and are completely lacking in controversy, but kids need to understand the wider implications of the journey. Columbus discovered America - discovered in the learned tradition, as in surveyed the area and mapped it out for future understanding.
The most important fact about Christopher Columbus is that he landed in the New World which began years of repression and decimation of Native Americans. Elementary kids are probably more excited to learn facts like the Nina, Pinta and Santa Maria. However, those aren't the most important things that need to be known.