If your primary reason to come to NY is to attend NYCC for 4 days, I suggest you get a hotel near Times Square, walking distance to the convention entrance on 38th St / 11th avenue. If you need to drop off purchases or take a nap, you can. Plenty of food options at night after the show. All subway lines intersect there so if you want to go sightseeing on other days, take the train.
Stay at a large full service hotel in Times Square. NY hotel tax is about 20% so be prepared.
Coach buses from all 3 airports are available and are your cheapest way to arrive in NYC but locating the bus in the airports your first time out isn't the easiest. Ideally, you should travel light if taking the coach buses. It's not a bad ride and will drop you off at the major hotels.
Car Service, Taxis, Cabs, Ubers, Lyft are most convenient. Since you cross State lines from Newark, NJ (EWR) into NY, the fare DOUBLES.
A regular yellow cab, taxi from LaGuardia (LGA) or JFK airports have a flat fee into anywhere in midtown Manhattan plus tolls. No meter rates. The taxi dispatcher should make you aware of that. LGA is the closest airport but the worst.
I would not take public transportation (train) from ANY of the airports. Why lug around all your luggage, trying to figure out where you are going? To save $20? Take the coach bus if necessary but not the train. During rush hour with luggage? Up and down the stairs? At night from Jamaica station? I have, it's not pleasant. LGA does not have a train option. EWR train is okay but bus is better option IMHO since they should drop him at the hotel.
Good luck Jay. Lol.
Cheers!
N.