Is it better for a Muslim to make definite supplications regarding worldly matters, such as offspring and success, or to entrust the matter to Allah, saying, "O Allah, choose for me, for I do not know how to choose"?

It is prescribed for a Muslim to supplicate to Allah and ask Him for his needs with certainty, without condition, just as the prophets Zachariah and Solomon (peace be upon them) did when they asked Allah for matters of clear benefit, such as forgiveness, mercy, and righteous offspring.

However, if one does not know whether the matter is good for him or not, it is prescribed for him to say: "O Allah, if this matter is good for me, then facilitate it for me, and if it is evil for me, then avert it from me," as in the supplication for Istikhara. Entrusting matters to Allah applies to affairs whose outcome and benefit the servant does not know, whereas matters of known benefit, such as forgiveness and mercy, are asked for with a firm, unconditional request.

In summary, there is no harm in supplicating to Allah for righteous offspring and other good things in this world and the Hereafter with a firm request.