I don't think that there's a "should" or "shouldn't" here - or that "Cinemagination" is any better (on the contrary, I'd say it's worse since it's much too long and unwieldy for a park name). For all I care, they could call it something completely uninspired, like "Dinoland", and I'd still go.... oh, wait....
Interesting - I hadn't really focused on the name as "cinema - gine", but as "cine - magine". But when different people see different things in your brand name, that hints at possible confusion (which is a potential problem).