This is the trio "Radioactive" by Imagine Dragons. Briley is on vocals, her brother Cal is on piano and dad Matt is playing guitar.
This is Ilse's improvisational composition "Mystical Sunset at the Beach." She created both of the ukulele parts you are hearing on this piece. Her teacher Elizabeth is playing the background part and Ilse is playing the melody. Improvisational means that the song has some planned parts (the background) but the melody Ilse is playing is unique each time.