There is a special 3 day hopper ticket that can be purchased for $99 each, up to 6 tickets.
There aren't discounts offered at the gate that i'm aware of, but if you go to the ITT/MWR on your base, they also offer discounts on other tickets. We just got our 4 Day Hoppers there for a pretty nice discount.
The military member has to be present when the tickets are used (in our 3 experiences, anyways) but they are not the only person that can use them.