Hiya, Stephanie! I have all sorts of advice, so I'll give you an overview, and then if you have additional questions I can help you with, come on back.
First, you'll want to consider accommodations. The largest regular resort rooms will be the family suites, located at
Disney's Art of Animation Resort. The maximum party size here is six, but you can request rooms that are close together. Some of the rooms are connecting, but those are not a guarantee.
To keep everyone together, look at
Disney's Deluxe Villa Resorts. These resorts have rooms that can accommodate up to 12 guests. They are more pricey than a regular resort room, but for a family of eight, you fit in a 2-bedroom villa. Villas feature full kitchens, plus a washer and dryer to keep up with the laundry, and at least two bathrooms.
Once you choose your resort, figure out how many days you want to spend in the parks. If you want to do all four days in the theme parks, definitely do a multi-day pass. You might want to add on the plus option, which will give you access to water parks, or consider a park hopper option if you think you might tackle more than one park per day.
The dining plan helps with the food budget - you'll get a feel in advance for what you'll be spending. That can be a great thing when planning vacation. There are three different plans, so you'll want to select one that works best for how your family likes to eat on vacation.
Good luck with your planning, and if I can help further, I'll be right here!
Anna