[humor] In light of the abuse scandals, we can all see the advantages of having ALL the boys in the parish serve. With them hanging around in groups of 10 or more, you can be 100% certain they won’t be alone at any time

[/humor]
It’s one of the most active things a pastor can do though, Most of the other factors are in the hands of God, or in the hands of the family.
The Parable of the Sower (Mk 4:1-25) should be of assistance in resolving your conflict. The call to the priesthood would be like any Grace God cares to bestow. For it to bear fruit, it has to fall on fertile ground.
A parish pastor can only do so much, but MUST do what what he can. That means
- By example and homilies, encourage the families under his care to pray fervently and often.
- giving strong homilies in favor of recognizing children as a gift from God ( so familes are of the size that GOD wishes them to be, and no smaller). Thus there will be more boys in the parish
- And doing what he can to take the boys that God chooses to gift the families with, and use the time he has with them ( Mass, breakfasts with the bishops, retreats at the seminaries) to put them among good seed, and not have the calling strangled out by the weeds that the boy will encounter elsewhere in life.
- Finally, since the pastor is not omniscient, he does not know which boy will be called, or when, so he should expose as many boys as he can to service at the altar. And do in such a way that a boy so called would have the clearest idea of what life as a priest would be like.
To do any less would be a failing, would you not agree?