Thank you all for your helpful responses. DH and I had a fabulous time. The weather was fabulous on Saturday, and a bit chilly on Sunday, but it never rained, despite the forecast. Our hotel room was fabulous, a NYC first for me. We ended up mostly riding Citibikes and walking for transportation, with some cabs. Highlights were the Gugtenheim, MoMA, Kinky Boots, Central Park, Highline, Empire State Building (DH sprang for express tickets!) and the gluten free donuts at Tu-Lu's. Plus some really stupendous dinners.
The shopping was fun. I bought a couple of cotton sweaters, and did a lot of looking and trying on. I went to Rag & Bone to try on the Dre's (BFs), thinking that they would contradict the Nordstrom recommendation to size down, but they agreed with Nordstrom that they should be fairly snug.
I was completely surprised at the large numbers of people wearing a) workout gear, and b) tight and fairly thin leggings. I saw very few people wearing relaxed skinnies, and almost no one in BFs. I even saw someone (who was otherwise very well dressed) wearing what appeared to be tights for leggings. In the shops, lots of SA suggested that I could wear tops with leggings, even sweaters that didn't cover my behind completely).
I didn't end up wearing the floral Nikes, but wore a plain black version, gold Paul Green sneakers, and my flat black Alberto Fermani boots. I felt a bit casual in the Nikes, but we were biking and walking, and they seemed to fit in with our activities.