Need last minute help -leaving tomorrow for
NYC. What is the best way to get from JFK to Grand Hyatt in Manhattan? Don't want to do the subway with all our luggage. The Hyatt can arrange a limo for $123 that can comfortably take all four of us with luggage. The alternative is to try to cram into one taxi? What would they charge?
Also interested in visiting Ellis Island. What is the best way to do that and is it possible to do without also doing the Statue of Liberty tour (which we are not interested in)?

If you have as lmuch uggage as I infer from your statement, then one cab probably won't be big enough for the four of you, unless you can get one of the station wagons that are now available in New York.
You can get a limo cheaper than $123. There are many reliable limo companies operating in the city that charge less. Two that I know of (but have never used) have easy-to-remember phone numbers: 212-777-7777 and 212-666-6666!
As for getting to Ellis Island, take the subway down to Battery Park, where you catch the boat. Staying at the Grand Hyatt, you are right next door to Grand Central where you can catch the subway. You do not have to stop at the Statue of Liberty. However, you do get a magnificent view of it en route to and from Ellis Island. Plan on spending a bit of time on Ellis Island. It's time well spent.

Good advice by Howard. I'd also consider the Grey Line vans/buses from the airport for approx. $12 per person.

For a listing of all options, check out

www.panynj.gov/aviation/jgtsfram.htm

Your best bet is a taxi. What everyone else on this post failed to mention is that a taxi from JFK to Manhattan is a FLATFEE of $30 per trip, not including toll and tip.
So even if you need 2 cabs, it will still be cheaper, and more comfortable than any other alternative.