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, sallallaahu ‘alayhi wa sallam, is His slave and messenger.
As regards delaying having children because of lack of provision, this is not a correct idea because the provision and livelihood of the fetus is already written while one is still in the womb of his mother. Allaah says (what means): {And there is no creature on earth but that upon Allaah is its provision, and He knows its place of dwelling and place of storage. All is in a clear register.} [Quran 11:6]
Moreover, Ibn Mas’ood reported that the Prophet, sallallaahu ‘alayhi wa sallam, who was the trustworthy and the one received the truth, said: “...The angel is then sent down to him to blow the breath of life into him. The angel is commanded to write down four matters: his provision, his life-span, his deeds, and whether he is happy or wretched.” [Al-Bukhari and Muslim]
Moreover, you should not delay having children due to Hajj especially since your wife disagrees with you concerning this. So, you should take the initiative to have children, and Allaah may facilitate matters for you and bless you with abundant provision and you would then be able to perform Hajj together with your wife.
Allaah Knows best.