Your children will be reassured of their individual places in your new family through actions more than words. Since your two children are with you every other weekend, it should be feasible to have time for your new baby and your wife when your children are with their mother. In the beginning, plan on focusing attention on their needs when the baby arrives and they are sharing you with your new son or daughter. Do not expect them to share your joy. But do expect them to relate to you.
Pacing is everything, so go slowly.
Let their affection evolve naturally. Let them know that they remain irreplaceable to you. Watch this report about showing affection to boys. Find out here. You should not rely on this information as a substitute for personal medical attention, diagnosis or hands-on treatment.