We are traveling to Bangkok in March with our three children (boys, 12 & 10 and girl, 6). Are expectations for dress while visiting temples the same for children as for adults? Skirts and shirts with sleeves are easy for my daughter, but I am wondering if my sons could wear long khaki shorts? We want to be respectful, but I expect some grumbling from boys forced into long pants in the heat.

If you visiting a regular temples then IMO it's fine for boys to wear shorts and t-shirts. However, if you are visiting a grand temple or a palace, like Wat Phra Kaew where the Emerald Buddha is located, then the boys should wear pants.

Hanuman is right. My boy also wore pants only when we went to Wat Phra Kaew. It is really a good thing to ask ahead before traveling. Be safe.

Worth thinking about getting some of those trousers that unzip at the knee and became shorts. You can therefore wear the shorts for comfort throughout the day but whip out the 'legs' from your bag and zip them on when the need arises.