When is it safe to travel with a baby by car?

brigette
So baby is due April 29 and my husband's family is having two weddings soon after. One is July and one in September. Either one is going to be a 6 to 8 hour drive and his family is really pressuring us to come. how hard is it traveling with a baby under 6 months? I read an article that babies shouldn't be in the car for that long since the can't gold their head up on their own yet. I'm going to ask my doctor, but I wanted other opinions too....