Your sons deserve to know why you are getting a divorce, but I agree it needs to be done respectfully. A guardian ad litem is assigned by the court, and is not there to support your husband's cause, but to advocate for your sons. At 14 and 17, the odds are excellent that their wishes will be respected, but they should not be essentially "tricked" into choosing one parent over the other without knowing the basic facts. The longer the reason why their family is imploding is kept from them, the harder all of this will be on them.