That Claire's baby is born within minutes of Boone's death is not a coincidence. Locke doesn't believe in coincidence. He believes in fate. There is purpose here. There is meaning.
At first he didn't understand how the island would be so cruel as to give him someone like Boone and then take him away. But he understands everything now. And, as always, Locke will do what is necessary.
It will be easy. Charlie trusts Locke with his life. Claire looks to Charlie, and why would she object to Locke? After all, he built her a cradle. Locke will rock the baby for them when he has woken up for the third time that night. Charlie and Claire will flash grateful smiles and stumble back to bed. Locke will feed him mashed oranges and carve him blocks, shooing Claire away for some 'alone time,' and Charlie will be able to play his guitar without worrying about sticky baby fingers. Locke will baby-sit, taking him for walks and teaching him to swim and track and hunt and fish, and build him a tree house, a secret place for just the two of them. Charlie and Claire will smile and nod and listen to his happy babbling, then hand him over to Locke. Each day he will spend more and more time with Locke, and each day Locke will take him out farther and farther, showing him more of the island and all of her secrets. No one will notice. No one will care. And one day, Locke will explain everything. His power. His gift. Who he is and why he is here. One day Locke will call him 'Boone'.
But that's a long time off yet. For now, Locke is content to be the hand that rocks the cradle.