Six Flags in New Jersey is found just off Interstate 195 in Jackson, New Jersey. It is one of the most popular themeparks in the United States so i would imagine it would be worth checking it out for yourself.
For detailed information on the theme park you should read the
Six Flags New Jersey article.
Seaside Heights is an area in Ocean County which is close to the theme park. I would recommend this as a place to stay if your looking for somewhere convenient. The article gives you details of the accommodation in Seaside Heights and hopefully you will find a hotel to suit your needs.