BVG timetable
To: Filmpark Babelsberg
Potsdam is in zone "Berlin C". Day ticket public transport for Berlin ABC is EUR 6,30.
Have a look into the history section of this park. Some films/series the theme park is made about are probably only known to the German speaking audience or the Non-English speaking audience (as these countries buy barely foreign films/series).
With children the park is a good idea. For adults if you don't have special interests in films or theme parks not a must. There are more important/interesting sights in Potsdam.