How many children should you have in Islam? One two three four or more.
There is no limit on the children we can have, whatever Allah blesses us with we thank Him. We are encouraged to get married to a wife who is willing to have many children (usually a women who herself was in a big family), and discouraged to getting married to one who cannot bear any children. It has been narrated that the Prophet (peace and blessings be upon him) said when a man came to him asking whether he should marry a women who cannot bear children, the man asked three times and the Prophet each time said no, on the third he said:
تَزَوَّجُوا الْوَلُودَ الْوَدُودَ فَإِنِّي مُكَاثِرٌ بِكُمْ
Marry the one who is fertile and loving, for I will boast of your great numbers
Sources: Islamic online university