Melatonin

Vi
I have a friend that has been giving her kids melatonin every night before bed for a little over 2 years. I am personally not a fan since I've heard some bad things about prolonged use of it.  Her kids stayed at my house the other night and she didn't pack it for them and the oldest one was fine, she knows she can fall asleep without it, but the other two (6 &5) almost threw a fit because they didn't get it.  I put them down and they got up 10 minutes later complaining they couldn't sleep.  I explained how sleep works and told them to close their eyes and stop talking (cuz that's what they were doing those 10 minutes). After I closed the door again, they were asleep within 5 minutes.  I REALLY want to see my friend's point of view with giving her kids the melatonin every night...but I really just don't believe in kids relying on it to help them sleep.  I can get the kids to bed without it...I think she just feels it is part of their routine and doesn't want to take it out and cause issues.  Anyone have thoughts on melatonin?