When I googled “Excommunication and divorce” I found this site which says:
Remarrying after a divorce without receiving a prior declaration of nullity (annulment) does damage a person’s communion with the Church, not because the Church rejects this person but because he or she has chosen a to live in a relationship that is in violation of his or her previous wedding vows.
The children of the first marriage are not affected by the excommunication. If they were baptized in the Church and have lived lives that are true to the teachings of the truth, they should be “in communion” with the Church.