If you're travelling with children, keeping them safe is your number one concern. Give them your hotel's business card when you check in, so if they get lost or need to find their way back, they will know where to go, or have an address to give a cabbie or police officer.
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Most hotels have business cards, but if you're staying in a hostel or Bed and Breakfast, they may not have one. In that case, write out the location's name, address, and phone number in the local language. You can even add a message along the lines of "Please take me to: [hotel's address]." Having it saved on your phone is great, but a hard copy is ideal — you don't want your child's safety to rely on whether their phone has been pickpocketed or their battery is working.
As long as your child knows to present the card when they ask for help instead of wandering around (and potentially getting more lost), they will make it back to you safely. It's a little tip (one you may consider yourself, in case your phone dies and you get lost), but it can make a big difference when you're abroad, lost, and alone.
General Safety Tips When Travelling with Kids? [Fodor's Travel]