I am sorry for all the harsh posts. I will do my best to help you understand the Church’s view on family planning and contraception:
The Catholic Church does not believe in the “have sex and see what happens, God will only give you what you can handle” mentality. On the contrary, the Church teaches that
responsible family planning is a virtue. A married couple is to prayerfully discern the size of their family, considering their obligation to prioritize God first, then spouse, then children, then helping the community. They must also, of course, take into account finances, physical and mental health, etc.
That said, the Church also teaches that artificial birth control - pills, condoms, spermicide, sterilization, etc - is sinful. That does not mean the Church objects to responsible family planning - as I said, the Church teaches that responsible family planning is a VIRTUE. The Church requires that each act of marital intercourse must be
ordered toward life, meaning a husband must climax and “spill his seed” inside his wife’s vagina. Couples may avoid pregnancy by limiting marital intercourse to the infertile phases of the woman’s menstrual cycle and abstaining from marital intercourse during the fertile phase of the woman’s menstrual cycle. This is called Natural Family Planning (NFP). NFP methods such as the Creighton Method (which tracks a woman’s fertile phase using observations of cervical fluid) and the Marquette Method (which uses cervical fluid as well as a fertility monitor) are 99% effective in avoiding pregnancy when used correctly.
The reason the Church teaches that all acts of marital intercourse must be
ordered toward life is that the two God-given purposes of sex - 1.) uniting of husband and wife as one body and 2.) procreation - must not be separated. Using pills, condoms, spermicides, sterilization, etc. blocks out the procreative aspect of sex because it uses man-made devices or medical procedures to prevent sperm from getting to the egg. When a man climaxes inside his wife’s vagina without any artificial means of preventing pregnancy, the act is “ordered toward life” because the procreative aspect of sex is not blocked out, even if pregnancy does not result, because no unnatural means was used to stop the sperm from reaching the egg.
I agree with the posters who said your wife may want to introduce your daughter and son-in-law to one of these methods. I personally recommend the Marquette Method because you can learn about the method through an online system which allows you to talk to the professionals who invented the system. They are available to help 24/7.
I hope this helps answer your question. If you still have questions, please feel free to send me a PM. God bless you and your family.