I'm sure it would be fun to join the family vacation, but traveling to Fiji with 4 month old twins sounds like hell. Jet lag for you and them, going up and down from altitude hurts their ears and stops up eustacian tubes (infection can result, that won't be fun in Fiji). How can you hold both if both are screaming? Feed them? How can you go in an airport restroom stall? You can't leave twins parked outside it. Manage an airplane toilet for yourself - leave them on the seat? Uh-uh. If you can travel with a family member who will help, maybe. Otherwise, it's an ordeal for you and them, not to mention fellow passengers who will want to kill you if this is all going on. Don't expect flight attendants to assist. They have enough to do without being babysitters. How to travel with two little babies? Don't.