One of the biggest misconceptions about Christianity is that once you become a Christian, you life is filled with rules and regulations, and suddenly you can't have any more fun. That couldn't be further from the truth. Today my family went to Six Flags and had a great time. The kids are tall enough to ride most of the coasters, and it's my 6 year-old daughter that is the biggest thrill junkie of all of us. It's so wonderful to sit next to her on the Mindbender coaster, go through a complete upside down loop, and hear her cackles and screams of joy next to me. Whenever we get off a ride, the usual response is "can we do that again?"
It is for freedom that Christ has set us free. (Galatians 5:1)
One of the main tenets of Christianity is that we no longer have to be under the Laws of the Old Testament. The rules of "you can't do xxxx" or "you have to do xxxx in a certain way" are gone. In Romans and Galatians the Bible talks about how we are not saved by the Law, but by Grace from God. Christ came in order to save us from the Law, not to put us under new and different laws. Christ came to free us from the shackles and chains of the Law. Really, Christianity is all about freedom!
Does that mean that we can do anything we enjoy? Nope. Sin is still sin. But there are a lot of things that people think is sin, but really isn't. And simply having fun isn't sinful. And when you think about it, sinful acts always contain a good chance of doing you serious harm (such as sexual immorality leading to disease and emotional hardship). God doesn't want us doing sin because of the pain it can cause us, not because He's a spoilsport.
Accepting Jesus in our hearts gives us incredible freedom that we did not have before that. And that freedom means that we can laugh, dance (yes, it's in the Bible so don't think you can't), joke around, enjoy movies (we're not supposed to conform to the world, but the Bible says that we are supposed to be a part of it), and go to amusement parks. Christianity is about joy, pure and simple. In this world it's pretty hard to grab hold of that kind of joy for long, so we need to embrace it when we can.
And if you don't think that laughter and glee are part of Christianity, then just look at my kids as they go hurtling down the drop of the Great American Scream Machine, see the happiness on their face, and tell me that God doesn't want us to feel that way.