Your numbers look right to me. Another option to consider though is to still do room discount on one room and free dining on the other and upgrade to regular
DDP. If you put 4 adults in free dining room and 1 adult and 3 kids in the other (just for reservation purposes), you would be paying 4 x 21 x 4= $336 and you would have 16 qs, 32 snacks, and 16 adult TS. You said you have 3 adrs so that would cover all of the adult's meals and you would have 1 left over. 2 kids could maybe split that remaining adult credit and you could pay for any other needed kids meals at table service out of pocket. This may or may not be a better idea depending on which restaurants you have booked (buffets or similar where you have to pay for each person) and the cost of kids meals.
Edited to add that you would still ha r the room discount for the second room in this scenario so the $200ish you would save with that would probably cover the kids meals that aren't covered under the first room's dining plan.