my suggestion is book a room at a standard hotel, think radisson / marriott / best wester... that you can book up to 4pm on the day of arrival. make sure its in a price range you are prepared to pay, just in case you need to use it.
Then try some of the bargain sites, like priceline.com (you can mangle an irish address and add a zip and state code), or hotwire.com / easyclick.com. I've used both and gotten great hotels for very decent prices in Midtown NY - but cross reference with betterbidding.com to give you some idea of what you may end up with.
i'd be wary of accommodation on arrival as if you mention to immigration they get all stroppy (had that experience on a package to Florida, where accommodation was advised after landing).