1st of all, b’sha’ah tova.
My boys are 23 months apart. We started preparing our older son for the arrival of his sibling during the 6th or 7th month of the pregnancy.
We loaded up on toys for our oldest son, so there would not be jealousy (in fact, the opposite, he viewed his brother as the reason he was getting toys).
We did not give all the toys at once, in fact, our “baby” is approaching 7 months, and we still have some toys put away. We give them whenever we see he is having a hard time due to the loss of all the attention.
We have our oldest “help” whenever he wants. This includes watching his brother getting a bath. He also knows that some times he helps by playing while mommy is nursing or changing a diaper.
Bli ayin hara, my oldest absolutely loves his brother, and our biggest issue is getting him to stop climbing on top of him to give kisses.
Much Hatzlacha