Transportation
The drive from Hanoi to Halong Bay is roughly 4 hours with a break of 15 minutes after the first 2 hours, the road is quite bumpy also. So for the most comfortable option for children, Discover Halong suggests you to book a private car. A shuttle bus of 16 seats is also quite convenient as it only contains up to 8 guests but not a good choice if you need a vehicle that can stop randomly. Company like Indochina Junk even has a luxury private car, which is renovated from a 16 seat-car to a 4 seat-car with super-comfy seats.
Room in hotel or Cabin on cruise with Extra bed
Usually for hotels and cruises, kids less than 12 years old are considered children. In principle, double cabin allows only one child sharing bed with parents. They often offer free of charge for child under 2 years old (considered as infant), and charge around 50% of adult rate for 1 child under 12 years old. Two children below 12 staying in 2 separated cabins are usually charged at 75% of the adult price.
If you are worry about your children, want to keep an eye on them, you can find a triple/connecting room or request for extra bed/mat, but keep in mind that not all rooms can afford the later as it depends on room area. For hotel, almost every 3-5 stars hotel can arrange extra bed but for cruise, it is harder as the rooms are normally smaller. So for cruise, search for connecting/triple cabin. Cruises with connecting cabins are easier to find than cruises with triple cabins. Moreover, connecting cabin is charge similar to two cabins with policy as mentioned in first paragraph. Please refer to our article about triple/connecting cabins to find out some cruises names that you can approach.