She is very courageous undertaking this sort of trip. The longest trip we took was melbourne to meribula when our oldest was 3 and she complained of a sore bottom. So depending what type of baby seat your friend has, she might want to invesitgate placing some padding into the seat for her baby boy. Jacqueline was in a booster seat so we placed a small piece of sheep skin (the real stuff) under her bottom for the next trip and that seemed to do the trick.
Otherwise, plenty of stops on the way to let him streach is legs and plenty of water for him to drink as i can only imagine it being a hot trip. This trip will probably take her longer than normal as she may have to do more frequent stops for her baby.
Wish her luck.
Vic, 2 girls - 9 yo & 17mth old