Sorry you're not getting any answers. I've not been to DLR on Memorial Day weekend in many years (pre-FP days!) so my answer is probably irrelevant. I did want to give you some sort of response and hopefully others with recent experience can chime in.
The crowds were so bad the Saturday I went that after spending a couple of hours just trying to force our way through the masses of people, my sister and I chose to give it up and we left.
I have no idea how things usually are now, but at that time, the DLR officially launched the summer hours that weekend and the crowds were intense--the worst I've ever seen in all the many many times I've been.