I'm a Prezi trainer, teaching people how to use the software.
If I understand this correctly, you have a big map, which is one file. And you want the presentation in Prezi to show appr. 8 points on the map and also the overview. The solution herein lies in making Prezi zoom to those places by adding invisible objects and not necessarily split the map into multiple objects. Can be done easily. If I wouldn't be broke right now I'd do it for free :-)