Danielle,
I am so excited for your 1st trip to WDW! Be sure to stop by Guest Relations & pick up a "1st Visit" button for each of you. When you get home, mark the dates of your trip on the back with a permanent marker for a great keepsake from your trip.
Walt Disney got the vision for Disneyland when his daughters were very young. He took them to amusement parks on Sundays, sat on a bench, looked all around & wondered why there couldn't be a better place for parents to take their kids & have fun together. His dream came true at Disneyland & that dream made its way across the country to Walt Disney World. I am thrilled to tell you that there will be many rides that the 3 of you can do as a family because that is exactly how Walt pictured it.
There will be some exceptions to this. Dumbo at the Magic Kingdom would be a bit of tight squeeze for the 3 of you in one Dumbo. But The Magic Carpets of Aladdin is the same premise & there are 2 seats in each ride vehicle. The Tomorrowland Speedway is also another that the 3 of you would likely be unable to ride together but if your DD7 meets the minimum height requirement of 54 inches to drive alone, you & your son could ride in a car behind her.
I'm not sure which parks you plan to visit, but if you let me know, I'd be happy to give you some ideas of specific attractions. Also before you go, be sure to visit the
Traveling with Little Ones section on the Disney World website. You'll find a list of attractions with height requirements contained in a PDF file on the right side near the top of that page. That way you'll know which attractions you won't be able to do and prepare your kids in advance & avoid disappointment once you arrive.
Wishing you many magical memories :-) Allison