If I sent my kids away as an exchange student I would request that they stay with an LDS family....I see nothing wrong with that. If they are in another country they will have plenty of cultural expierences regardless of religion. We had a female exchange student with us from Latvia for a year. She was not LDS and I told her if she wanted to attend a church of her religion to let us know and we would see to it she got there. As time went by she started attending with us every Sunday. She would get up and get ready on her own. She is back in her country now and we miss her dearly.