I was 22 when my parents separated. I can tell you I feel like it was as bad on me as it would have been if I were young. If your wife moved out, I am sure they know. Even if you tell them, your kids are probably not going to run to your W and tell her how they feel.
Don't put them in the middle. Trust me I was put in the middle and have some resentment towards my mother for doing that to me. They shouldn't have to deal with that. It made me feel like it was on my shoulders. If I made him feel guilty enough then he would come back to her.
Do you really want your W to come back because your kids gave her a guilt trip?
