Here the truth------credits are put directly on to your card---room key, park enterance, dining credits all on on card----now the thing is all the credits are put on all the cards. If you have 4 people staying 5 days, each card has 20 credits. When you use the credits by giving your server a room key, if 4 meals were eaten then 4 meals are taken off all cards w/out needing to scan all 4 cards individually. This was handy for us because we were split up a few days and it would not have been ideal if we had only one card to use. We also did on one occasion pay out of pocket for the kids meals to have credits for a 2 credit TS meal (I asked the server 3 times if it was ok and if I should have any guilt over trying to beet the system, he assured me over and over again it was fine.) I was completely honest as to what I was doing asked if I could and then asked again if there was any rules prohibiting me to use it like this. I would not have if I was told not to or even if I was told you can but really shouldn't.
Anyway bottom line credits while on each persons card individually, are still pooled and can be used anyway you the purchaser sees fit. If you are not sure if you are using the credits the right way ask a CM---they were always very very helpful.
Have a great trip!