It's true that your IP address is no secret. It's a basic part of internet communication protocols to send your IP address whenever you connect to another site, request a web page, chat, play an online game, etc. Without your IP address, the computer on the other end wouldn't know where to send the reply.
But that doesn't mean that Evildoers can find your house if they know your IP address. Each time you go online (if you have dialup) or each time you start your computer (if you have cable or dsl) you will be assigned an IP address, randomly selected from a pool of IP's assigned to your Internet service provider (ISP). WHOIS Your ISP
So a person MIGHT be able to get a general idea of your geographic location, based on your IP address, by doing a lookup on the WHOIS database, but that will only tell them the physical location of your ISP -- not YOUR home address.
And if you use a large regional or nationwide ISP, the IP lookup probably reveals nothing of interest. For example, if you are an AOL subscriber, your IP address lookup will show the location as Dulles, Virginia -- regardless of where you live.
Of course there is an exception to every rule. If Joe or Jane User calls your ISP and wants to know who was using a certain IP address last Tuesday, the ISP will tell them to go away. But if an officer of the law hands your ISP a court order to reveal that information, they must do so. Your ISP's logs will enable them to determine which customer was using a certain IP address on a certain date & time, and they must reveal that information if a court has found probable cause that a crime was committed by that person.
But for the truly paranoid (or the criminally inclined) there are ways to surf the web anonymously. The Anonymizer service will act as a proxy between you and your ISP, and they claim that your information cannot be subpoenaed because they do not store it.
The same concepts apply to your email address. The part that follows the "@" sign is your ISP's domain name. And given the domain name, one can determine the ISP's physical location, but nothing personally identifying about the email user without a court order.
Web-based email accounts are not truly anonymous, either. Even if you don't provide your real name when signing up, they can capture your IP address and track you through your ISP if necessary. Other Considerations
It's much more likely that you or your children will reveal your physical location the old fashioned way -- by just blurting it out. Kids who chat or play online games should be reminded often that they should never reveal any personal information, including their last name, phone number or home address.
Oh, and if you have any spyware or viruses on your system, all bets are off. These things are designed to violate your privacy.