You can park for free on Sunday almost anywhere. You didn't say what time you were arriving, but you can park in the 30's near the Garden for the entire day with no fee. Walk to the nearest subway and the city is at your fingertips. I recommend below 34th street for parking and be willing to walk a couple blocks. Will easily save you 40-50 dollars. As a general rule, summer Sundays in NYC offer plenty of parking spaces as most residents are out of town on weekends and return Sunday night. Also the last 2 weeks of August are usually the quietest weekends in NY along with the week prior to Labor Day. Enjoy all that NYC has to offer. PS: If you only have a few hours, and you want to entertain and educate your kids without them knowing it, the Museum of Natural History/ Hayden Planetarium would be a lifelong memory for them. It is on Central Park West in the seventies, easily accessible by subway from the Garden area and would be a blast for the kids and a great area to explore and get some kid friendly food at a not touristy price if you walk west toward Broadway. You can then take the number 1 train back to the Garden for the event. Have a great time.