With or without the DDP, you really do need ADR's...especially for the most popular establishments. And the DDP would definitely not be worthwhile if you could not get into any table service establishments.
Are you saying you don't want to make ADRs at all? If you plan to do any table service restaurants, I'd definitely make ADRs well in advance, or you'll likely be unable to get in anywhere that you want.
I've been to WDW many times and have never made any ADRs. If I can't get a table, I just do counter service. But I have a friend who will be going to WDW for the first time in June for her honeymoon. She booked a package thru AAA including the DDP thinking it was a good deal but said she didn't want to make any ADRs because she didn't want to be tied down to any kind of schedule. I tried telling her that I didn't think it was a good idea but since I never used the DDP I wasn't too sure about how those credits work.
It is not the best value without the ts credits being used as TS credits.Also, with no adrs made it may be extremely limited to near impossible to utilize the dp to its fullest potential. So I would tell her make at least a few adrs or skip the dp.