I think you'll be fine. We drove from Melb to Adelaide when dd was 3 months old without a problem. We stopped every couple of hours for food, air, and a stretch, but she slept most of the driving time. If you're worried she'll get bored they have those things that stretch accross the car seat with bobbly things to play with, or you could hang something obove your littlie's head.
My best advice is take snacks, water, and follow your bubs cues, but you should be fine.