Before you talk to them make sure you are saying what you really feel because the thing about kids is they know. So line up with what you are saying. They aren't really old enough to understand totally - but the 5 year old is probably able to understand well enough. Be real with your kids. Tell them that you and dad changed and just aren't in the same kind of love any more - you love each other like friends now. You know, tell them how you feel and be real - that's the best advice I can give you.