We've used the DP twice (once paid for, once free) Both times the credits where all pooled. The first time we actually ended up using "adult" credits for a few kids meals as my mom and I shared a few TS meals. I don't bother tracking "adult" vs "child". Also, we have left the world both times with unused snack credits even after treating strangers to ice creams. And we've filled up several bags on our last day for airplane food, etc. to use up our last CS credits.
The first time we used the plan it was brand new (Jan. 05) and there was some confusion using it. What's CS breakfast? inc. dessert?, etc. I learned after we returned that we were allowed dessert with CS-didn't realize it and didn't get it. Last time we used it there was less confusion (Sept. 05) however, we even had different experiences at the same restaurant. At Kona we ordered the filet two different times. The second time we ordered it our server asked if we wanted to add the scallops-it's included in the DP. Of course we did. Our server for the first meal never mentioned it. So, if you wonder what's inc. don't hesitate to ask. Scallops at Kona, smoothies at Park Faire, etc. Remember, the higher the bill, the more tip the server receives. They get 18% of the total bill (as if you were paying it) therefore the higher the bill, the higher their income. JMHO