Mrp Alert is probably a member of a mileage-earning program other than JetBlue TrojanHorse, so Long Beach airport not really an option.

Personally I always think flying into LAX is best cuz usually more flights, bigger planes for upgrades, cheaper fares, more centrally located, lot of cheap airport hotels, but that's just me. Find the cheapest fare you can get & then get a car rental.

For those coming in for Sat/Sun only, I'd definitely pick LAX area because then you've got access to (free) shuttle to Manhattan Beach and you can catch the cheap Big Blue Bus to Santa Monica, both of which are two good things to do on a quick weekend. Anything more than that & you'll need a rental car (although if one of the folk in town gets one you all can car pool).

Edited to add: Whether you do a dinner in LAX area or Long Beach area, there will be rush hour traffic on the Friday night. Saturday not really. Personally I'd pick Long Beach for Sat as more people might be coming from up north & that would make it easier for them.

Also, for those in from out of town who want to do some things in Long Beach on Saturday day, there's the beach, the Long Beach Aquarium (part of which is outside), the Queen Mary, etc.

Cheers.