Just my 2 cents, which probably isn't even worth that, because I've never been to DLR, but.....the "Unofficial Guide" said that Nemo is not a good choice to ride first thing because of how long it takes the ride to load, and the length of the ride. UG says you could waste 30-70 minutes of precious early morning touring time by doing Nemo first. They recommend going during a parade or fireworks instead.
Does anyone agree or disagree with this? I would like to know, because we definitely want to ride Nemo during our trip.