It is very easy to find Santorini Park as it is located on the main road heading to Hua Hin. They used to allow free entry on weekday, however, I just went there last Friday and they are now charging the entry fee even on weekday.
There are lots of parking spaces available and you can have fun taking a picture with your love ones. There also some machine for the little kids such as a carousel (the fee is around USD 7 per 5 min. ride, if i'm not wrong), ferris wheel, big water ball that we can go inside, for teenagers such as G-Max Reverse Bungee, G-Max Giant Swing, Wallholla, 4D movie, etc.
There is a new attraction called Trick Art Museum (entry fee around USD 9) where you can take a photo with 3D background. This trick art museum is very popular in Korea.
There is a newly opened Santorini water park located in the same area as Santorini Park, however, you have to pay entry fee separately from Santorini Park but it's worth the money for the family with kids.