There is a slight element of uncertainty that the next day could be fully booked la.
The ship I stayed has individual bedrooms for couples. If you travel alone then you may have to share if they are full. Dinner is prepared by ship's cook. And they cruise through the small atolls in the afternoon and have drinking parties at night. So you can check specific details when you look for deals.
Departure wise you really have no choice. Because halong bay can get seriously crowded if you arrive mid afternoon. Take it as you travel earlier so to skip the crazy crowd.
I have the unfortunate fortune of seeing a Vietnamese boy drop his pants and shat inside the heritage site because it was too crowded to get out and go to the toilet. Like WTFBBQ. and the parents just laugh and joke about it.
Reason for not choosing the 2D1N one is that not interested in some of the activities. Did ppl sit out on certain activities? Not interesting in the cooking demo too LOL.
the 2nd travel agency replied, it's cheaper at USD105 per pax for car, minvian transfer max 8 pax is USD89.
7.15 - 7.30 Pick up
09.45 board Cruise (2 hrs+ to reach Halong Bay??!!)
Itinerary is lunch, visiting Magical Sea Cave, kayaking, Swimming, Ba Hang floating houses, cooking demo, sunset party, tea break
OR
08.30: Pick up
Midway rest stop in Hai Duong City, arts and crafts center
12.15 board Cruise
Itinerary is lunch, Hoa Cuong, Ba Hang floating houses, kayaking, Thien Cung cave, cooking demo
http://www.centralbackpackershostel.com/halong-hideaway-tour--2-day-1-night-.html
This is the one I took. The departure was 7.45 though. They have the Sapa hiking trip too. Now that I highly recommend! Especially if you can tahan 5,6 hours of hiking through very beautiful valley.
The hostel was quite cheap too. 5 usd a night. Include free breakfast and a one hour free beer at night.