We're booked with 35% off at a standard room at Poly, which seems like a great deal, so I understand you not wanting to lose it.
In our case (only 2 adults), the 35% is saving us $1300 off the room. Dining Plan costs $900, and with gratuity and snacks, our food cost with the Dining Plan is ~$1200. OOP, though, our food cost is only ~$950. So, for us, the 35% makes the most sense.
With a family of 4 (2 adults/2 kids), the dining plan is $1200, probably putting your food costs around $1600. Your OOP cost might be around $1400. Only you know for sure, based on what you'll eat.
Anyway, NUMBERS. But the point is that you'll probably want to take a close look because you might find that a free dining promo looks very similar to your 35% off promo.