Couple of my points:

Money: I am surprised that nobody mentioned withdrawal from an ATM. Please don't make me believe that Canadian banks do not have ATM/Debit cards. While all banks in Vietnam add their fee when using overseas cards, local AgriBank adds just 1$ equivalent (other banks add $2-$4) and HSBC does not charge additional fee.

The best exchange rate you can get is at gold shops. Exchanging money at the airport won't give you good rates.

What to do/see - up to you, but honestly, anyone suggesting Tunnels need to be treated with a suspicion. Because these tunnels have very little to do with reality or history. If you want to see the city, it might worth to check at TripAdvisor with local student groups offering tours around the city for about $20.

Couple of safety tips: do not walk next to to road with backpack or purse - bag/purse snatching is endemic. Recently there was a story at TA of a girl who was dragged on a road by a motorcyclist couple hundred of feet when he tried to take her bag. She ended up in hospital with 40 stitches.

Also do not flash your camera (do not carry it on stripes, but always put inside a bag) and you phone - never put a phone on a table in front of you when you stop by for drink/meal.