If your child begins to get sick or queasy from the heat, have the child lie down in a cool, shady spot and give fluids. If this doesn't help, seek medical assistance. Children need constant fluids to avoid heat stress.
Water is ideal, but lemonade, fruit juices, snow cones and popsicles also are good choices.
Avoid caffeinated drinks. The sun and heat can be deceptive. Liberally apply sunscreen before heading outdoors. Use a sunscreen developed specifically for children because the ingredients are less irritating. For older children, an SPF of 30 is fine.