If you are just having a trial separation, I have some advice for speaking to your child. About the separation and the upcoming changes.
You want to say something like, “We have something to talk to you about. Please don’t interrupt… We, your parents, were having some difficulties living together. We have made the decision to have a trial separation for three (or six months) to see if we can work out the problems in our marriage.”
The rest should be the same. The children must know that you both love them very much and that they are not at all responsible or to blame for the separation or divorce. Marriages or partnerships end or need a period of separation because of the parents – never because of the children. Even if you have a developmentally disabled child, a special needs child, or a physically disabled child, it may put stress on the marriage, but many couples find a way to hold on to each other even under the most stressful circumstances.
Likewise, many families have very easy children, plenty of money, friends, and great families, and they still fall out of love with each other or the marital bond gets broken. I say this, because I can’t emphasize enough the importance of making sure your children know that the separation is not their fault and that they are loved by you both very deeply.