Hi,
When you want to request a specific room or area, most people tell you to inform the cast member making your initial reservation so it's noted on your confirmation slip and then fax a room request to the room assigner at the hotel 5 days before you arrive. Generally you should be very nice and unassuming with the room assigner since it's not a given that you'll get your request. If you've made arrangements through a
travel agency you should ask them what part of the hotel they booked you in. There's the north garden wing, the south garden wing and the tower rooms. Both wings are 3 story buildings off to the sides of the tower. The tower is the tall 14 story A-frame unit that the monorail glides through. The tower is more expensive than the wings but I prefer to stay in the tower. Of course it's all a matter of personal opinion. I've heard others say they prefer the quiet tranquil setting of the wings. If you stay in the tower a lot of people ask for a Magic Kingdom view as high up as you can get. The Bay Lake side is very nice too but you don't have the Magic Kingdom view. There's nothing like lying in bed at night and watching the castle change colors.
I love the Contemporary. You'll find that people either love it or hate it. There never seems to be any middle ground. There's tons to do there and it's all in a compact area. Other hotels on Disney property are spread out and it's sometimes a long walk to get anywhere but not at the Contemporary. Especially if you stay in the tower. Many say that there's not a lot of theming there but it's all in how you look at it. I love it so much that I never want to stay in any other hotel. And I have tried a few of the other hotels but most of the time I just think about how much I miss the Contemporary and how I want to be back there.
As far as tips go, be sure to watch the Electric Water Pageant that comes around nightly on Bay Lake at 10:05pm, weather permitting. Your 3 year old daughter will absolutely love it. Also, look for the Mickey ears out back that light up at night. A lot of people stand inside the ears and have their picture taken. If you're up for a boat ride you can catch a launch in back of the hotel at the dock. It will take you to the Wilderness Lodge, Fort Wilderness Campground and then back to the Contemporary. There's a walking path from the Contemporary to the Magic Kingdom and it's generally faster to walk it than to ride the monorail since the monorail has to stop at the Ticket & Tranportation Center, the Polynesian, and the Grand Floridian before it gets to the Magic Kingdom. The path takes about 10 minutes and its very pleasant. On the flip side, the Contemporary is the first stop that the monorail makes after leaving the Magic Kingdom. The elevators in the hotel are very cool. Each elevator has a different Disney character announce your floor when you arrive. Last tip is to look for the 5 legged goat in the mural on the Grand Canyon Concourse. Ah, just thought of one more thing. While you're waiting for the monorail to arrive, ask the monorail attendant if your daughter can ride in the front car. If there's no one else waiting you, she, and the rest of your family can ride up front with the monorail operator.
Most of all, have fun and enjoy yourself.
Usually it helps to request to in your category, if you request the tower, you should have a tower room booked, otherwise it is a upgrade, complimentary or payed for? Mostly people request views, floors, near elevator, etc.... 
