strmtroopr96,
All the cards for each room will have access to the dining credits for that room. So, you should be able to give your DD's card to your parents and they can use their card and your DD's card. Just make sure they tell the server what credits to charge on each card. My children's cards worked for dining credits, but not for regular charging. I don't know if they automatically do this, but I remember requesting it at check-in.