I wonder if you want to go all the way down that path? A children's story about ill-fated lovers who take their own lives is doomed to failure. Why not take some of the other elements of the story, if you must base your story on feuding and family hatred, and aim at a loving, romantic, happy outcome.
But you said "children's book" not "young adults" so perhaps even a romance would be inappropriate. It'd hardly be a best seller -- unless you placed it in the animal kingdom and had two bunnies eloping.
Or you could try the poetic approach. I don't know who wrote this piece: 'Twas in a restaurant they met, Romeo and Juliet; He had no cash to pay the debt So Romeo'd while Juliet.