Here's an interesting video for kids on an endothermic reaction being used in an Air Force lab to create fuel from aluminum and water!
If you're looking for an experiment this week, you can use the old baking-soda-and-vinegar experiment, but first, test the temperature of the vinegar first. Ask your kids to form a hypothesis of what they think will happen to the temperature when the baking soda is added, then measure the temp after. You can even do the experiment in a plastic bag and see if you can feel the temperature difference. (No, this is not my idea; credit belongs here.)
And this one offers definite "I love homeschooling" points: Use this experiment to make ice cream in a plastic bag and demonstrate an exothermic reaction! The reaction of the salt with the ice lowers the freezing point of the ice. Anyone else a fan of experiments you can eat? (Tip: They use milk in this experiment, but I've heard half-and-half recommended elsewhere.)
Here's one other exothermic reaction experiment using steel wool and vinegar.