The themes of the poem 'Paper Boats' are innocence (the child's simple act of floating boats with hopes), imagination (imagining clouds as playmates and fairies sailing in boats), and playfulness (the playful act of sending boats down the stream). 'Ignorance' is not a theme—the child is imaginative and aware, not ignorant. 'Travel' is not a central theme; the boats represent dreams and hopes rather than actual travel.