Prudential concerns are very important to look at. No matter what we love our kids. However, kids need time and attention. They have real, tangible needs. Kids are resilient but if there is an inability on the part of the parents to be able to be present to them and to guide them it can cause harm. This is a real concern. If a couple knows they do not have the time, attention or energy to care for another child and they conceive because they don’t want to use NFP I think there is not wise. Yes, we always welcome children but if we do not have the resources to care for their emotional, physical and spiritual needs it can be detrimental to them. Yes, some parents manage to keep it together despite very limited resources. It sounds like you have a serious reason to avoid a pregnancy but using NFP is too much of a burden. I understand how hard that can be.
The other side of the issue was pointed out by Bl. Pope John Paul II, who did not find himself in a position to chide married couples who were having too many children:
"…*In the sacrament of marriage, a man and a woman—who at Baptism became members of Christ and hence have the duty of manifesting Christ’s attitudes in their lives—are assured of the help they need to develop their love in a faithful and indissoluble union, and to respond with generosity to the gift of parenthood. As the Second Vatican Council declared: Through this sacrament, Christ himself becomes present in the life of the married couple and accompanies them, so that they may love each other and their children, just as Christ loved his Church by giving himself up for her (cf. Gaudium et Spes, 48 ; cf. Eph 5 :25).
In order that Christian marriage may favor the total good and development of the married couple, it must be inspired by the Gospel, and thus be open to new life—new life to be given and accepted generously. The couple is also called to create a family atmosphere in which children can be happy, and lead full and worthy human and Christian lives.
To maintain a joyful family requires much from both the parents and the children. Each member of the family has to become, in a special way, the servant of the others and share their burdens (cf. Gal 6:2; Phil 2 :2). Each one must show concern, not only for his or her own life, but also for the lives of the other members of the family: their needs, their hopes, their ideals. Decisions about the number of children and the sacrifices to be made for them must not be taken only with a view to adding to comfort and preserving a peaceful existence. Reflecting upon this matter before God, with the graces drawn from the Sacrament, and guided by the teaching of the Church, parents will remind themselves that it is certainly less serious to deny their children certain comforts or material advantages than to deprive them of the presence of brothers and sisters, who could help them to grow in humanity and to realize the beauty of life at all its ages and in all its variety.
If parents fully realized the demands and the opportunities that this great sacrament brings, they could not fail to join in Mary’s hymn to the author of life—to God—who has made them his chosen fellow-workers*…"
— Pope John Paul II, homily, Oct. 7, 1979
[Of course when he referred to Mary’s hymn, he meant the Magnificat:
*My soul proclaims the greatness of the Lord;
my spirit rejoices in God my savior.
For he has looked upon his handmaid’s lowliness;
behold, from now on will all ages call me blessed.
The Mighty One has done great things for me,
and holy is his name.
His mercy is from age to age
to those who fear him.
He has shown might with his arm,
dispersed the arrogant of mind and heart.
He has thrown down the rulers from their thrones
but lifted up the lowly.
The hungry he has filled with good things;
the rich he has sent away empty.
He has helped Israel his servant,
remembering his mercy,
according to his promise to our fathers,
to Abraham and to his descendants forever.]
Couples have to use their consciences to decide if they can welcome more children, yes, but generosity is a good thing, where it is possible.