Will need to investigate the Dependent issue closer: While you may be able to get an ACA policy for him..
A BYU Missionary & taxes publication...filled with gobbledygook, indicates that missionary work is not included in the "temporary absence" for college type of rule (starting at the bottom of labelled page 248....page 17 of the PDF, below). OF course, if the son was a student in college for the first 5 months, plus some time at home in the year before going on the mission....then the first year of missionary work may allow you to claim them as a dependent.
But there are a ton of other qualifications.....you might be better off seeking advice from the LDS main missionary board in SLC (even local boards may be misinformed). They may have issued a simpler advice document on claiming a Missionary child as a dependent, and in what situations it may be allowed or not.
<a rel="nofollow" target="_blank" href="
https://digitalcommons.law.byu.edu/cgi/viewcontent.cgi?article=1531&context=jpl">https://digitalcomm...>
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
