I think you need to have a firm, but loving conversation with your MIL about boundaries. If you are concerned about teaching your children humility and reasonable limits to spending - this is blowing it out of the water for you. There may come a time when funds are tight and a large, frequently updated wardrobe may not be possible. By then, they'll be accustomed to this type of lifestyle and the transition may be difficult. I've experienced this and resentment can build when spending changes.