How about using the coins? Make them unable to change the coins because one side is defaced - ground down and etched with lines. When they examine the coins more closely they realize that they have a jigsaw puzzle. You can even take the map, print it on some paper, and cut it into coins for them. Overlap the coins and get the map.
What about etched into one of the potion bottles so that it is not revealed until the potion is consumed. Or you could make the cork of a potion a rolled up map.
How about using the coins? Make them unable to change the coins because one side is defaced - ground down and etched with lines. When they examine the coins more closely they realize that they have a jigsaw puzzle. You can even take the map, print it on some paper, and cut it into coins for them. Overlap the coins and get the map.
What about etched into one of the potion bottles so that it is not revealed until the potion is consumed. Or you could make the cork of a potion a rolled up map.
Good luck.