Top of the rock is fantastic views!
For the helicopter tour I'd recommend sunset, it's stunning. If you can get a doorless one then it's an incredible view and feeling - not sure on your budget but you can get a private one too.
Walk the highline down to Chelsea market - los tacos is incredible, pop to the pizza bar Filaga (incredible). There's a delicious gelato stall there too. Hudson yards is lovely to wander around too!
Rubirosa does amazing pizza and pasta and is very classic tiny New York restaurant, would definitely recommend.
I'd get the subway across to Brooklyn, wander about dumbo and walk back over the Brooklyn bridge for the best views imo.
Wall Street bull is cute too for good luck! Statue of Liberty is a classic too. Definitely Central Park but don't get sucked into a horse carriage ride. Hire a bike if you want to be speedy around it! 5th ave is a classic and nice to walk down and see the sights, St Patrick's cathedral is unbelievably beautiful.
If you want to see a ball game the subway will take you direct to Citi field to watch the mets, such a great night out and the atmosphere is electric. Same for the basketball!
We enjoyed just getting the subway and wandering about, loved the Chelsea area - blecker street pizza is delicious too.
I think we did 20-30,000 steps a day depending on the day and absolutely loved it! What time of year are you going?