Eligibility

I’m trying to help my friends from Italy to buy the jr pass for 2 adults and 2 kids (12 years old, 9 years old). They’ll stay in Japan for 10 days and thinking to buy 7day jr pass. Can they get stamps on passport as “temporary visitors” for sight seeing when they enter Japan even though they will stay there for only 10 days? I learned that the stamps are needed in order to exchange and activate the jr pass.
Also one kid is 12 years old, Japanese site said 12years old is considered as kid but English site 12 years as adult. Which one is correct? They are leaving less than a month, so I need to find out as soon as possible. Thank you.