Vietnam - hints for holiday in Hanoi

[Junket]

we're planning to spend ten days in Hanoi in August with our three and seven year old daughters. We've previously visited Thailand and Singapore with great success. But I think Vietnam is in a different league. Your experiences/advice on safety, what to do/see, avoid, very welcome.Flight distance is not a consideration as we will fly from the middle east via Bangkok.

Vietnam is a country where companies in my area post employees to. Many of them won't take their families because it is heavily polluted and particularly bad for dioxins, (partly residue from Vietnam war) which are all through the food chain. Don't know if that is relevant to a holiday, though.