yes, it is expensive...
we're also going for 3 weeks in august 2017 - with 8 of us (don't ask how much it's costing.....a not so small fortune)..
initially, i was going to have us stay off property to save money, but when i calculated in the cost of food, i realized that the savings weren't as great as i thought they'd be...so i made reservations with disney.uk for the 'free dining' package....
it will be more expensive, but everyone really wants to stay on property, plus with two toddlers this time, it will be easier to get back to the resort for the midday nap this way...
but if you can get a really good deal off property, that works too...we've done that in the past..
but now with the cost, we'll only go to disney about every 5 years.....so given that, it's worth it to us to splurge and stay onsite...