How fabulous!!! Since this is your first time, and you want to get the most 'bang' for your buck. I would suggest first pick when you would like to arrive. I would suggest that you make reservations during the Value Season. This is when the room rates are at their lowest.
Value Season: January 1 - February 13, August 3 - October 1, November 30-December 18
I would first go to
www.waltdisneyworld.com and begin the reservation process, by inputting the dates you would like to arrive and depart from Disney. It will then go through a 'processing' and you will get another screen with all of the resort hotels. Scroll down to any one of the 4 Value Resorts. Since you have a grandson, I think he might enjoy Disney's All-Star Sports Resort. It's all about sports. It is a value hotel. It's the first stop for the bus in the morning and the first stop coming back from the parks, at night. So, lets just say you want to stay at the All-Star Sports Resort and you click on it. You will have the option to pick a dining plan or not. Since your grandson is only six, I wouldn't recommend the dining plan. It's a lot of food and you may not get your money's worth.
I also wouldn't recommend Disney to book your flights. You could probably save yourself money doing it yourself without the middle person. You will be required to put a $200 deposit. I also would recommend purchasing the insurance, because you never know if something should happen, and you can't go, or a hurricane, or any number of things, you will be able to get your money back. You will have to pay the vacation off in full 45 days prior to arrival as well.
Hope this gives you a foothold to start. Have a great dream vacation with your grandson. Heather M.