I was in BKK last month for 6 days and did not see one mosquito. I was out most evenings and took boats on the river and still did not have a mosquito sighting. That being said avoidance is the best measure to prevent Dengue Fever (as Malaria is not a risk). One thing to keep in mind is that the Dengue Fever mosquito bites both at day and night and is more prevalent in urban areas. So if you notice large bodies of standing water in the gutter or on the sidewalk or after a rain storm be sure to put some repellent on and avoid those areas if you can.

While Dengue Fever is not a pleasant experience, it is rarely fatal (3% case mortality rate). It does require lab tests to diagnose, so knowing where the best English speaking hospital is may be helpful in the event of any emergency. Looking at the CDC website for signs of Dengue Fever may be helpful to give you an idea of what to look out for.

In BKK especially be on the lookout for dehydration as you will constantly be sweating. I did not pay attention to this and actually fainted in my hotel room because I was so dehydrated and consequently lost a day of vacation as I rested. Bottled water is cheap, so make sure you buy and drink plenty (and make sure your kids to as well). If you can, buy some sports drinks (Gatoraid or Poweraid) and make sure to increase your salt intake. Salt is crucial for water retention and as you sweat, you lose a lot of salt.

Lastly, to avoid the Bangkok Belly I took a dose of Pepto Bismol every morning before heading out for the day. If I ate a particularly questionable or greasy food, I took another dose. My 6 days in BKK and the entire 3 week trip in SE Asia went fine with no upset of the stomach.

Enjoy the trip! I am sure it will be a blast!