You find a lot of money exchanges in the city area. However, once you enter the temple’s premises, there are no money exchanges. So, you should convert the needed money before you board to the amazing place of Lumbini. You also can tip the people who guide or serve you by any means. Well, you do find money exchanges when you are in Lumbini outside the temple's premises. However, on the inside, you won’t find any money exchange. So, it is suggested to convert money before you board to Lumbini. You can do that while you are in Kathmandu.