Hi Tina!
I am so excited for you and your family! Planning a Disney vacation is a lot of fun! You are correct, it is a good idea to book dining reservations as early as you can. Disney allows dining reservations to be made up to 180 days in advance.
The calendar for the park hours and extra magic hours for December is not available yet. Right now Disney is only showing park hours until August. So check back with us in May and you will find what you're looking for.
To find the daily hours and extra magic hours for each park just go to the Disney website (www.disney.com) at the top of the screen you will see the PLAN heading. Point to it and a screen will drop down with the heading "Plan your Walt Disney World Vacation". On the right of that screen you will see a list of the parks. Click on a park you are interested in visiting and a calendar will appear with the park hours and extra magic hours for the month of December. If you click on a day of the week you are planning on visiting that park the scheduled times for the parades and fireworks for that day will appear as well.
Making dining reservations can be done one of two ways. You can do it on line on the Disney website. The link for dining reservations is located under the "BOOK" heading. Or you can call (407)WDW-DINE.
Being your first time at Disney you will want to pick up a free "1st time at Disney pin" for you and your family. You can pick up these pins at guest relations in all of the parks.
Have a magical time and happy planning!