I just recently returned from Disney and had the DxDP. We were a party of nine with 2 reservations. The plan was put on one reservation with 3 adults and 2 kids. The other had no plan, all adults (well 2 real adults and 2 in Disney's eyes). As people have reported, credits were pooled and I had no problem whatsoever using credits for all the adults and paying OOP (when monetarily beneficial) for the kiddos. Further, the kiddos were almost always offered to order of the adult menu or get adult-sized portions of kid menu items.
Some highlights:
I found that contrary to what I was expecting and heard on here from earlier reports, I was advised by the server at almost every TS meal about the adults being able to get adult drinks. I'm guessing after doing it for a couple weeks it became part of their routine. The exceptions were breakfasts, Ohana, Boma, and Wave notably. However after asking we were able to get Mimosas (with POG at Boma and Ohana - Yum) or Bloody Mary's (or anything else for that matter).
I won't name where due to not wanting to get anyone in trouble but there were a couple occasions where the server didn't bother to segregate the seats and so second adult drinks ordered by the adults were "comped" by the plan. Both times I had a TIW ready to pay for the additional drinks and was told "no other charges, just the grat" (auto-grat party of 9). When I looked surprised she said, "I ran the plan and it took it, I didn't make the rules Disney did. I'm not about to separate that many seats." I know this isn't the norm (and wasn't) and only happened a couple times but thought it was worth mentioning.
California Grill brunch we were allowed to get a Bloody Mary in addition to the included Mimosas on the plan. That surprised me.
Tusker House ROL package we were offered adult drinks.
California Grill dinner any glass of wine/sparkling/champagne was included. Items you couldn't get were clearly marked (high end shots mostly).
The last night we couldn't eat much more food so used some credits at QS (Captain Cooks). We were allowed to take an unopened can of beer with each one.
In conclusion, in my experience it seemed like the servers were very laid back about giving the drinks or anything else for that matter. It makes sense to me as the more they allow on the plan the larger tip they'll get (especially in my case with parties of 9 and auto-grat). The other conclusion, I don't know how people can get the DxDP on one reservation. It was my first time ever on any
DDP and my goodness was it so much food! We had a hard time sharing it across 2 reservations!