Yes! Your spouse and unmarried children under 21 are eligible to receive the green card when you receive your EB-3 green card.
You are the PRIMARY applicant. Your spouse and children are DEPENDENT applicants.
Your spouse and children are added to your application process during stage 2, the I-140 stage.
During Stage 3, the Adjustment of Status or Consular Processing stage is where your spouse and children will complete their own permanent residence application as your dependent.
If you are inside the U.S. in legal status and applying for Adjustment of Status, then your spouse and children will each complete their own Adjustment of Status petition to be filed with USCIS. You should all receive your permanent residence green cards around the same time, after the I-485 petitions are approved by USCIS.
If you are outside the U.S. and applying for Consular Processing, then your spouse and children will each be entered on your DS-260 application. You should all receive your permanent residence approvals at the same time, after the successful consular interview at the U.S. Embassy or Consulate.