Do not pack light regarding clothes and shoes. Pack lots of medicine, as there is some disease in Vietnam. Though you can buy clothing in Vietnam, none of it will fit you. The Vietnamese love westerners, be prepared for lots of questions and your children will be adored, especially if of fair complexion as it is so different. The roads are chaos: thousands of motorbikes carrying families, fridges, pigs- its madness. Also, crossing the road takes extra care as bikes do not stop; they go around you. Not for the faint-hearted. It will be very hot and humid especially further south so bring hats and lots of water (6000 dong for a liter bottle is a good price - about 15,000 dong to $1 and you can use both currencies). Haggling is good fun and even water is to be haggled for. Always approach it with a smile.  Wet wipes/anti bacterial dry hand wash is always recommended and take a toilet paper roll for when you are out and about.  Bring on portable bathrooms if you are prepared.