Download "advanced task killer" and look at all the apps running in the background. A hot phone means a LOT of stuff is running at once. You'd be amazed at how much crap activates in the background and is just hogging up resources. Use that app to identify the apps running and then uninstall every app you don't use often or can't live without. I guarantee your kids have like 300 apps installed and use 10 of them regularly. Then get a good app cache cleaner from the market and clean your app cache out.
My Bionic never runs hot anymore, I've got my task killer set to crazy and all the bloat apps uninstalled, all apps that I don't use uninstalled or disabled. App cache cleaner is set to clean every day. Phone runs nice and cool and snappy and battery life is amazing.
Having facebook and flickr and tumblr and twitter all going at once like my wife does... that'll heat up a phone lol. And she wonders why our phones are identical and mine gets twice the battery life and is so much faster.