8 yrs kids could be doable with little effort . If you really want to go, they will adjust in a little while. Language is main thing if they don't speak Nepali, but they will learn pretty quick.

My kids aren't 8 yet, but one my firends daughter is very much interested in Nepal , culture and language . They didn't have any trouble settling down back in Nepal . Try to keep environment similar to here for first year or so. Mainly decent school, less crowded location and gathering, may be AC and stuff at home if possible. But also let them integrate slowly. May be telling them we will try and see how it works , if doesn't work, we will come back will ease their pain. I personally fell we should make this decision before kids are 6.

But I have to tell you that this theory of one have to go back to their own place to be truely happy is not entirely correct. Human race has always been migrating, adjusting life style over the history of human life. Ofcours your kids will live life in American way, but isn't that why we came to US. If we can't accept that then we will be pain all the time.