Have you tried the co-op with her? It's actually really good in this game.
Created a dedicated two-player save file and am starting a new playthrough from scratch with my daughter right now. You're right, the two player mode is actually really good. It's actually much easier, in fact. Especially the bosses. Since I've already beaten it, I'm playing as Mario and her as, Cappy, and it's working out really well.