Moshi Sleep Stories.
It has meditations, soft music, and sleep stories for those having a rough night, or who need to calm down, you can go night swimming with yawnsy, dream hopping with nodkins, and enjoying a beach club with yoyo! It is a wonderful series that is so soothing. (just to name a few, there is almost 100!)
A few of these stories are on youtube, but the full app does cost money, so please speak with a trusted adult first!