For what it's worth, my DD (who is now a sophomore at William and Mary...non military) participated in serveral of these "leadership conferences" in high school. The following is VERY much just my opinion, but here goes:
Good programs, but in terms of "weight" given for college, not alot. Every one of DD's friends received the same invites. These are "for profit" organizations and if you have a checkbook, you may attend. Period. And they are NOT cheap!
Having said that, they are good programs (or at least the two that DD attended were) but you can acheive the same or better in terms of experience by taking advantage of of other opportunities such as:
Senate/Congressional Page (my DD did this and it carries a LOT of weight)
Girls State/Boys State
Model Congress/Model UN
Internship (paid or USUALLY unpaid) at the local office of your congressman
DD has double major in International Relations and French w/ minor in Econ so that is why she particpated in so many of these types of things in high school.
In other words, your student can take advantage of opportunities (such as the above mentioned) that carry a LOT of weight and are free or relatively inexpensive or in the case of senate/congressional page, you actually earn a stipend! (at least in VA). Caveat: these are usually competitive programs and can require a good amount of work for the application/vetting process. One advantage of the leadership programs that you asked about is that they are not competitive....fill out an app, write a check and off you go! Again, your DD or DS will enjoy those and WILL get something out of them but IMO there are better options but those require some work and planning! Hope my OPINION helps!