"Melko pienen tytön silmissä ei tarvitse loistaa"

should be: Melko pienen tytön silmien ei tarvitse loistaa" This makes no sense.

"mutta he tekevät!"

That constuction is not used in Finnish. You would repeat: mutta ne loistavat.

Otherwise, you cannot easily translate those lyrics into English. One is the Finno-Ugrian language, the other belongs to the Indo-European language family. The neighborhood of Sweden, lasted more than 1000 years, has of course had a deep influence... so F. is not so far from the Indo-European languages as you could think.

Otherwise, your translation makes no sense. :)