I have now experienced the special lines for 4+ PH passes, and it could not have gone smoother. In fact, I was surprised at how short the lines were both at DL and DCA for me and my spouse.
The first time we used it, we printed our names on the back of the tickets, showed ID, and were in. In DCA, we simply showed the ticket and ID and that was that.
A couple with children were in front of us and they simply asked the parents to print the child's name and their name on the child ticket and would verify it via the parent's ID. No child was asked for an ID at any time from what I saw.
There were plenty of CMs available and I asked them which lines, they pointed them out, and I was on my way.
This has really been much ado about nothing, IMO.
Something you said made me remember something from our last trip to DL November of last year. We put our names on the back of our 4 day park hoppers, including our 4 year old daughter's. I can't remember if they ever checked our ID, but on one occassion going through the DCA gates, the CM looked at the name on the back of our daughter's ticket and then asked her what her name was. If a 4 year old is going to truthfully say their name, I guess that is ID enough.