About using valid ID card for applying library card, is this type of ID card valid (see link below)? My daughter was rejected by using her ID card when applying, it's suggested that she should use her Kela card. I was surprised that this type of ID card is more official than driving license and also can be used as travel document to other countries but why it's not valid for applying library card?
Any photo ID that s issued by police is enough when applying library card. Passport, ID card of any EU country (the one you linked), Finnish driving license and Kela card with photo are all valid. Here is the Helmet listing about valid ID:s.
Children under 15 need a written consent of their guardian when applying library card. Read more at Helmet Library user regulations.