Hold a Treasure Hunt at distance

How to hold a Treasure Hunt at a distance with your grandchildren.
“My grandchildren hid cards with letters on at various places around their house or garden and then wrote riddles to give a clue as to where the cards were hidden. They then video-phoned me and read out the riddles and I had to guess where the cards were to be found. They took the phone round the house/garden and showed me the card if I had found the correct location. I noted the letter on the card and when I had deciphered all the clues had to work out an anagram from all the letters to make a word (for example someone’s name or a place name). After that, I did a treasure hunt for them in my house. You can make the clues as easy or as difficult as you wish depending on the ages of your grandchildren!”