All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
Hajj is an immediate obligation for whoever is physically and financially able to perform it, according to the view of the majority of the scholars ; this is clarified in Fatwa 91223, so please refer to it.
Therefore, if you and your wife are able, then you are obliged to take the initiative to perform this great pillar of Islam. The fact that you will have a baby is not a sound reason for not performing Hajj. You may take your child with you, and intend Hajj or 'Umrah for him, because our righteous predecessors used to do so, as reported by Ibn 'Abdul-Barr and others. You may also leave your child with trustworthy people who would take care of him in your absence and during your travel.
However, if it is not possible to take the child with you and it is not possible to leave him with someone else, then it is permissible for your wife to delay the Hajj, as in this case she is considered unable to perform it. As far as you are concerned, you must hasten to perform Hajj as there is no connection between your ability to perform Hajj and your wife being unable to go.
Allaah Knows best.