Game of Thrones - child actors

This first caught my attention - it's same story as Harry Potter series. Most amazing thing with Harry for me is how producers found child actors for main characters. They predicted that franchise will be blockbuster and other book will also be adapted. Just think for a while how hard it was to find a appropriate child among thousands of casting participants. Child not only talented enough to cope with main role today, but also after another 5 or 10 years.
With Game of Thrones producers  got to cast several child parts and series will be continued to the end of story, in my opinion. Of course, if Martin will get his ass to the keyboard and write two last volumes. But even for now, story is complex enough for next 3-4 seasons. For every child starring it's really long time. How will they grow up? Will they still match played characters as it is now? Guys and gals from casting department had tremendous job to do. I think they deserve praise. Just look how playful and wild Maisie Williams as Arya is. how her eyes sparkle. How elegant, posh is her sister Sansa, played by Sophie Turner. And this is they first flick!

Nina Gold, Edward Said and Robert Sterne are responsible for that outcome - thanks!
Unfortunately they also made some mistakes. If it comes to children I think that they made one mistake. Jack Gleeson as Joffrey Baratheon is in my opinion a miscast. I imagined him as a very good-looking, tall and with curly hair. Handsome and spoiled at the same time. I'd even say rotten to the core. But maybe that is just me.
What do you think about it?