In the original story tinker bell only had a life span of 3 weeks. So he just banished her for a third of her lifetime. Of course this was also the same Peter who would regularly kill his own lost boys if they failed a task too often, decided he wanted to play the part of the pirate, were unable to lose weight if they gain too much to fit into their assigned entrance into the tree, or was in a bad mood and just wanted to fight. But it's alright he promptly forgot all about them and just found new ones to replace them.
I hate when people say he killed them. The book NEVER says he killed them it says he thinned them out. Most believe it means he banished them or sent them to the world where they are from. Or they became pirates or even part of the tribe that Tigerlilly is from.
Honestly would the other kids stay with Peter if they knew they be killed when they reach a certain age?
Well here is the thing about that see originally tinkerbell is described as so small she can only hold one emotion at a time. And her hatred of Wendy was a big one for her tiny body so she went for the biggest thing someone angry can do which is kill the person making them angry. It is also why when you say you dont believe in fairies one dies. Because they become so sad they die of sadness.
Honestly would the other kids stay with Peter if they knew they be killed when they reach a certain age?