Free dining would save you about $155/night [$58.66 per adult + $18.88 per child 3-10 years old].
Your dates are peak season. Garden view at Poly is $558 + 12.5% tax=$
$627.75 week night. Free dining would save you 25% ($155/$627.75). You can often get 30% room discount at deluxe so you would have to see what might be offered for room discounts.
If you were to get a garden view room at POR with a full price room at $221 + 12.5% tax=$$248.63. Saving $155 with free dining here would be a 63% discount. You wouldn't find a room discount that high.
At the value resorts you would get free quick service worth about $110 [$39.64 per adult + $15.75 per child]. A standard at Pop would be $145 + 12.5% tax =$163. So free dining here would save you 67% ($110/$163). You could pay the $40 per night difference to upgrade to reg DDP so you would be paying about $203 per night compared to $248 per night for a moderate that gets you reg DDP.
I really love the Poly but I don't think I could pay over $600/night for a room there.