If you're willing to drive 6 hours or so, I would say go to Busch Gardens Williamsburg. It has great roller coasters but enough rides for everyone else in the family as well. We would always take a 4 day trip there over my spring break. There are pretty cheap, and nice expensive hotels around too. Same with Cedar Point in Ohio although that's a little further away.
Another place would be Hershey Park. We have gone for Easter a few years and they do a really nice job. It's only about 2 and half hours from NJ. The water park won't be open, but there is more than enough to do. There's the whole main theme park, Chocolate World which is a little ride to show you how chocolate's made, and you get a free candy bar!, botanical gardens, i think there's a horserace track, a stadium so there may be a concert going on, and various sporting events near the theme park. There hotel's work kind of like Disney where there are 3 that are owned by Hershey, but there are others near by that are not. We have always stayed at the Hershey Lodge, and I highly recommend it!
Have fun!