You don't need to order a combo at a CS restaurant. The menu board shows combos, but you can just get the protein, or just the side. This is a big money saver over the course of a week. Maybe your family can share 1-2 orders of fries instead of everyone getting them. The kids meals that come with a toy, you don't have to get the toy. Saves $1.50, I believe.
WDW is a little smaller than 2x Manhattan Island. Think of walking from the Battery to Harlem. Keep that in mind when you consider transportation times on the buses, boats and monorail. Also consider that when trying to understand how much you'll be walking, in the Florida high heat and humidity. Buy moleskin and Bodyglide. Bring Band-aids.
You don't need insect repellent...Really. Don't wander off sidewalks to explore the natural surroundings. There's lots of hidden wildlife of the unlikeable sort. Bring non-drowsy allergy medicine. Florida plants might kick up allergic reactions. Things like bread and pastries don't last very long unrefrigerated. Because of the robust natural jungle-like environment, don't wear perfume and cologne. It makes you seem like a big flower waiting to be landed on by a variety of bugs.
Keeping in mind how big WDW is, that explains why staying on-site is 1,000 times better than offsite, even considering the price difference. Remember Disney has free parking, free transportation, and the property is all beautifully landscaped and Disney themed. It's like being in a special world, some people say it's a "bubble." Off-site free shuttles are infrequent and usually only drop off at the TTC. Off-site is far away. If you're not driving, it's hard to get to off-site restaurants. If you're driving, you pay for Disney parking every day. When you try a Disney resort on later visits, you'll kick yourself for those times off-site.