We grew up speaking Welsh in various places around the world. With my father that is, we spoke English between us (three sisters) and with my mother.
This is still the same today.
We were always aware of how proud my father was to be Welsh and how important it was to be part of that culture.We were taught to want to be a little different, not to want to be part of the herd. When we came home on leave we would attend a Welsh medium school.
The only resentment I felt was more to do with having to take Welsh lessons in my lunch hour as they were not part of the curriculum in my boarding school!
My sisters are married to a Korean and a French man respectfully and their children speak those languages as well as English (not Welsh unfortunately-they feel bad about this but don't live in Wales and are following the commonly given one person/one language rule.)
I have 2 children and speak Welsh with them (as does their father.) I am so proud to be Welsh that it does not cross my mind that they will 'turn their back' on Wales.
I have seen other people's children start speaking English to their parents at vulnerable moments but note that if the parents stand firm and continue to talk their native language the children desist. If the parents 'weaken' then all is often lost-a huge huge shame!!
My dh's brother moved away from Wales and after a lifetime speaking Welsh to all his family now speaks English with them. My dh is very angry about this and refuses to speak English back, but his mother now speaks English to him after 24 years of speaking Welsh. How weird is that!!??
Also think that role models are ver important. We are in constant touch with confident succesful educated Welsh speakers which makes a big difference to how a language is perceived both by speakers and 'outsiders'.
Please don't let a language or culture slip through your children's fingers. Even if they waver as impressionable children they will always regret their lost chance as adults.
(I know a girl who is taking A level Spanish and finding it difficult. Her mother is a native Spanish speaker and never spoke it with her. Tragic.)