Small group, a lot of road, but worth it! We are a family of 4 (9yo and 6yo) and we did it with a 5th person plus the guide and the driver.
By far the best and most beautiful part of Vietnam. Wild, sleeping at a homestay (the second one not so much) and seeing the beauty of the Ba Be lake and waterfalls,
Food was abundant and although the guide did not speak good english it was nice.
Be aware that most of the trip you are in a van driving never-ending twisted roads, but it is worth it.