Hey Bob! How wonderful to be planning your three year old's very first trip to WDW! Actually WDW itself can offer you every bit of information you need and I'm so glad you came to the Mom's Panel to get started.
First, I highly recommend going to
www.disneyworld.com At this site you are able to look at every resort. There are pictures of resort pools, rooms and common areas. You can also find out resort pricing at this site. Once you have a resort in mind you can either book on line or call 407- WDI-SNEY. I personally enjoy booking my reservation over the phone, call me old school but it allows me to ask any questions I might have about my upcoming vacation.
So reservations are made and now it's time to plan your days, this too can be done on the site. Each park is on the website. You can look at attractions and decided which parks interest you and your family the most. I feel pretty confident that you all will spend a lot of time at the MK, but remember there is truly something for everyone at each park. I also always recommend the park hopper option when you go to purchase your park tickets and definitely try to book a character dining for your three year old's first trip.
I hope this helps to get you started, but please know we'd love for you to come back to the panel with any questions you might have as you begin to plan your vacation. Thanks for the great question and best wishes planning your vacation.