Airplane and kids

So me and my man want to visit his parents out of state In Georgia . We live in Los Angeles , we have a 7 yr old , 1 yr old and a two month . Will we have to take car seats for both our babies ? Or do they have to sit on the lap ? Is it still too early to take my 2 month old on a plane ? We already planned to leave at night because thats when our babies sleep the longest so they wont be crying and be fuzzy the whole ride there . Any advice would be appreciated.