Efrat, as I worked in the airlines business before, I have to give you one advice - check each air company pet rules before you decide which one to use. Book the little furry guys in advance, long in advance. Some companies do not agree with the cats in the cabin, some do if the pets are in special carriers.
Good luck! I hope my favorite gang of Brits and Gucci will like to live in US. Maybe they'll get to meet Peanut and Tubby, and Lady Edwina