WE do it all of the times and it's never a problem. Often during our trips we are on the
DDP, but meet up with local CM friends for some meals. They get their CM discount on their OOP meals and we use our DDP credits. Just tell the server what you are doing at the beginning and they will make sure they bring seperate checks. In the spring we were a group of 5, us 2 on our DDP, our 2 friends on their DDP, and 1 friend paying OOP using our DDE discount, plus us using our DDE discount on drinks, now that was alot of receipts and bills to pass around the table. Keep in mind for this year, most likely your OOP bill will have the gratuity added, so keep an eye out for it on your OOP bill.