Most counselors will support a joint parental communication to the children about the pending divorce. However, a joint discussion about divorce with the children does require that you and your spouse be able to maintain a basic level of civility, if for no other reason than to maintain your children's peace of mind. If you and your spouse cannot be civil, do not attempt to discuss this issue together with the children.
If your marriage has been rife with conflict, your children may be aware of or even welcoming the relief of a parental separation and/or divorce. Do not be surprised if you find out that your children know more than you thought, even if you have been attempting to conceal the conflict from them.
The issues that your children want to be reassured about involve where they will live, where they will go to school, whether their activities and daily lives will be disrupted, and the degree to which they will be able to maintain their relationship with each parent. Teenagers can be particularly vulnerable and sensitive to disruption in their lives and schedules. If you are able to work out a parenting schedule with your spouse, it is acceptable to share that with the children to reassure them. It also can be acceptable to involve the children in the process of setting a schedule. However, that issue can be very delicate. You do not want children dictating to the adults and you do not want the children to have limited contact with either parent.
Above all else, do not discuss marital fault issues or the reason for the divorce with your children. Even if you think that your spouse is the worse miscreant on the planet, that spouse is your children's parent. Your children want to and are entitled to love both parents. That a spouse cannot make a marriage work does not dispossess them of the right to be a parent. More important, it does not dispossess the children of the right to love that parent and have a relationship with the parent.
Consider that you may have a range of reactions from your children about the pending divorce. They may not be surprised. Or, they could be upset and shocked. In many cases, even when they are not surprised, the children might be angry or blame themselves. Work with a professional to address all of these emotional reactions. Your children will adjust to your divorce, if you provide the proper guidance and assistance during that process.