Thanks for the suggestions.
How about this
HCMC 2 nights
dancing 2 nights
Hanoi 2 nights
Ha Long Bay 2 nights

Based on my experience, I'd recommend three nights in Ha Noi and only one at Ha Long Bay. Two nights at Ha Long Bay is overkill; take a day cruise and do not spend overnight on the boat. I'd also suggest spending a couple of nights in Hue instead of Da Nang (I assume that dancing is an autocorrect error).

Should i spend an extra night in HCMC ? 4 instead of 3 ?

There really is no reason for 2 nights in Halong Bay. Four destinations in 8 nights is just not reasonable.

That depends on your interests and how long you wish to spend at places that you visit. We were able to see just about everything that interests us and even do some shopping in two days in Saigon. If you wish, spend another day touring villages up the Mekong delta or visiting the Cu Chi tunnels. I echo SanDiego1K's suggestion to visit Hue instead of Hoi An. Even if you do decide to go to Hoi An, two nights and a day and a half of sightseeing are more than sufficient.

it's more about chilling because we will already have quite a bunch of domestic/regional flights, so i would not add more stops in our trip, especially as we will be with our 7 yo daughter and she is not very patient with transportation

Another time in Vietnam we'll do Danang, Hue and Phu Quoc but for now we'll stick to Hanoi, Hoi An and HCMC (getting to Halong already takes a full day, 4h round trip + the day cruise).

Btw, I was wondering if the driver would go faster on the highway to Halong or if the 2-hour drive is incompressible

In case that you are unaware, Hoi An does not have its own airport, the nearest airport is in Da Nang, approx 20 miles / 30 Km away, so it makes sense to visit Hoi An and Da Nang on the same trip. Hue is about a three hours drive from Da Nang and it has a nice modern airport.

I know it well ;)
It's just that this time we don't want to spend time in Danang and Hue

Ever since i had my daughter, traveling is way more laid back. Before that, I would cover every single corner of a country during a single trip. Now i usually split every destination in several trips

Covering the north, center, and south of the country in a single trip doesnt strike me as laid back. But to each their own...

Depends entirely on the driver and how fast they're comfortable driving. Also, there are some sections that are generally around an overpass that don't have a smooth transition and my driver slowed down to walking speed. Other cars were flying past us. These slowdowns add up.

I am thinking about having a private car with driver rather than using the pickup service at all hotels before getting to Halong, such a waste of time.

We had a private car with a guide and a driver. From the Sofitel Legend Metropole Ha Noi hotel it took 2:15, not including a 30 minutes "rest stop" at a tourist trap pearl farm, to drive to the dock at Ha Long Bay.

good to know, thanks
Now i need to find a good quality day cruise which does not stop at any kind of floating seafood improvised market or does not waste all day in kayaking or snorkeling stuff so that R/T transfer + cruise would not last a long day so that we would avoid being exhausted once back in Hanoi in the evening

https://www.flyertalk.com/forum/luxu...l#post31636846

https://www.flyertalk.com/forum/31826946-post40.html

Jade Sails seems to have nice boats