Hello Kimberly, thanks so much for your question. I think you will find that one night at Walt Disney World is simply not enough. After one day in the Magic Kingdom you will likely want to just move right in to Cinderella Castle Suite. If I were in your situation, I would most definitely buy a second ticket and enjoy another day in the parks. Your choice will ultimately be dependent on your budget, interests, and schedule.
Downtown Disney is the home of some amazing and unique shopping opportunities like the world's largest Disney Store, Lefty's - A Left Hand Store, and the Art of Shaving, among many others. I personally love visiting The LEGO Store and Disney's Pin Traders. There are so many great choices for dining also. One of my favorite things to do is go for dessert at Goofy's Candy Company and get a chocolate and candy covered Mickey Rice Krispie bar from the make-your-own-treat area, or picking up a chocolate covered pineapple. My mouth is watering just thinking about them. Another thing you might like to try at Downtown Disney is Splitsville Luxury Lanes. It boasts a diverse menu that includes sushi, pizza, rice bowls, and burgers as well as two floors of retro bowling fun.
On the other hand, you could purchase extra tickets and hang out in one of the four parks for an extra day. If I had only one extra day, I'd spend it in Disney's Animal Kingdom. It's my favorite park in part because it makes conservation and wildlife a high priority, while also being a fantastic resource on animal knowledge. And let's face it. Animal Kingdom has
DINOSAUR which is one of the best attractions, in my humble opinion.
Either way you decide to go, I think you will be able to find plenty of magical places to experience. If you need anything else we are right here waiting to help in any way that we can. Have a "pixie-dusted" Walt Disney World vacation.