If changing hotels is an option, stay at Park Lane. You will be in reasonable walking distance of more than you can see in three days, so transportation won't be an issue. Just try to avoid Leona.
If art deco architecture is of interest take a tour of Rockefeller Plaza.
If opera is of any interest, The Metropolitan Opera is as good as it gets. Even if you have only a minimal interest in opera, the Met is so good with sets, lighting, etc., not to mention the actual singing, that it is worth the evening. Also you can get reservations to have dinner at the theater before the opera and mark two things off the wish list. The food is good, and it's "moderately fancy", but not world class if that is what you are looking for. The Met is a 10-15 minute walk from Park Lane, so this is the one event you might want to take a cab for. I am not good at hailing a cab, so I give the bellman a 5 to do it for me. I probably tip too heavily, but I find that if I have a pocket full of 5's and give out one or two as appropriate, I can get willing help as opposed to people treating me like I'm a pain in the ass. Planning ahead for $100 in fivers, added to the cost of the trip makes my time much more pleasant.
I'd take good shoes, rather than roller skates, to Guggenheim. If you decide to go there, watch any documentary on the building itself and/or Frank Lloyd Wright to pique your interest.
Check weather.com and pack accordingly. Last time I went there was a freak blizzard and I was happy I took long undies.