Polygot toddler wants to learn another language. Are there disadvantages?

My daughter speaks English, Portuguese and Italian but her love of Studio Ghibli and Hello Kitty have piqued her interest in Japanese. My concern is that it’s SO different from her other languages… I don’t want to overwhelm her. If anyone has experience with this, I’d appreciate some advice. And for Japanese speakers, any recommendations for age-appropriate learning tools for a toddler. So far she really enjoys listening to Japanese music in the car and has been trying to sing along. Her father and I do not speak any Japanese 😅