Every time we go back to my wife's hometown in Indonesia, the children complain about the facilities there. How do we teach them?

Make the complaining an opportunity to teach gratitude and respect, not a reason to scold. Children used to comfort are naturally surprised by a simpler house, hot weather or a different bathroom. Before leaving, tell them what they will find and stories of their mother's childhood there. Give them a role, such as helping their grandmother or looking after younger cousins. Correct them privately if they complain in front of relatives, because those words can hurt the hosts. Parents, for their part, set an example by not complaining. The Prophet ﷺ said: “Whoever does not thank people has not thanked Allah” (Sunan Abu Dawud 4811). See educating the family.