We need some help. Our son does some geocaching with his American pals. This summer, he and several of his college friends are going to Europe, going different directions. They are planning several meet ups in European cities. They think it would be fun to use their mobiles and do geocaching in different towns. Is this a good idea ? Do Europeans know about this game ? Will people get upset when the kids are snooping, looking for the geocache ? We do not want him to get into trouble. Advice, please.