Yes, men under the age of 18 can do Exodus 90 and any of the Day 91 spiritual exercises with proper guidance, council, and consideration. Seek a trusted mentor, priest, or adult role model who can lead you through both the discernment process of taking up an Exodus spiritual exercise as well as guiding you in a spiritually and physically safe way through the exercise [exercises] itself.
The following things should be understood and considered before taking up Exodus 90 or any of the Exodus spiritual exercises:
FASTING AND ABSTINENCE FOR MEN UNDER 18 YEARS OF AGE
In accord with the spirit of the law and acknowledging the minimal abstinence and fasting called for in the Exodus 90 spiritual exercise, young men in good health ages 14-18 should consider their ability to participate in the food related disciplines of abstinence and fasting (In accord with the Church's wisdom and laws on fasting, those under 14 years of age are advised not to take up the food related fasts). Before taking up fasting, those under 18 years of age should ask the Lord in prayer if he is calling them to take up these disciplines, assure they are in good health, and seek the council of a trusted guardian.
No young man should be forced or negatively pressured to take up the food related disciplines of abstinence and fasting. Young men should be informed and guided, then empowered to make this decision freely.
All men who are not physically able to take up a given practice need not choose another discipline to replace it. Rather, they should increase their efforts to live out the disciplines they are able to do with greater consistency and love.
Young men who are in the midst of an athletic season or have a job that includes strenuous manual labor should seek council as to what aspects of abstinence and fasting are prudent for them and when.
COMMUNICATE WITH YOUR FAMILY
Going through the ninety days quietly, trying not to let others know you are fasting and praying daily is a virtuous thing. Though, a change in a man’s way of life will inevitably effect those around him. Thus, it is important to make communication with those around you, especially those you live with, a top priority before you start Exodus 90 so they too know what to expect.
Proper space and guidance is needed for young men to be a healthy fraternity. Fathers of the men should give them both space and guidance to bond, share, and challenge each other.
The fraternity of young men and older men will begin each weekly fraternity meeting together. This begins with step one of the meeting, praying together the opening prayer provided in the Weekly Meeting Guide. After the opening prayer and before step two of the meeting, the field report, take just one to three minutes for a man to recast vision for the young men and old on one relevant topic of Exodus 90 (i.e., Why have you come to Exodus 90? Why is it necessary to surrender to God? Why do I need to check in with my anchor?).
If young men have the space to be vulnerable and they feel respected when sharing their struggles in the fraternity meeting they can grow more comfortable talking about them as they strive to be freed from them. Once more comfortable with talking about such things with their peers, they are more likely to share those struggles with their father, if they aren’t already doing so.
It is hard for young men to avoid a pitfall they cannot see. It is important that proper guidance is given them. The possible pitfalls of pride (thinking we can earn God’s grace or achieve our own freedom) as well as fear (doubt or despair that we will fail the exercise or never be free men) all need to be pointed out and explained to them. Give the young men an understanding of how these different pitfalls might present themselves along the way so that they are able to see them and call them out for each other when they come up.
Be there for the young men as a guide, but view yourselves as brothers going into this spiritual wilderness together.