Just print or write your address on a sticker, or use one of those address labels you get randomly in the mail, and put it on the back of your cell phone. (Don’t want to show off your address to the world? Open up your phone case and stick it inside there. Just make sure the kids know about it.)
If you haven’t talked with your child about how and when to call for emergency help, we have a whole guide to that here.
Now, it might seem silly to expect that a kid who is old enough to read an address label might not remember their own address, but it happens, especially if they don’t need to tell people their address very often and aren’t in practice.
While you’re at it, consider asking grandparents and other caregivers to use address labels themselves—either on the phone, or by posting their address in a known area of the house. That way, if a kid ever needs to call in an emergency at Grandma’s house, they’ll know where to find the address if they recall it from memory.