As far as I know, you can only put your PSN ID on one System at a time.
Anybody looking for New Little King's Story, Grainger Games are selling it for £29.99 which is £5.00 cheaper than the PSN price. Amazon don't actually have it at the moment, there is just a 3rd party seller asking for £49.99. Looks like it could be a very limited run as a physical release.
http://www.graingergames.co.uk/games/ps-vita/vt39-little-kings-story