Can Military family (mother & Siblings) travel at a discount? (airfare only)?

Yes, just have your Son/Daughter purchase the tickets with their military discount. They can put the tickets in any name.

as a military spouse i've never been able to get a discount, even if there is it won't be much

That would be a policy that changes with each airline.
Go to orbitz or expedia.com and find out which airlines travel to the airport you want to go to, and then go to each of their web sites to see if they offer a military discount.
If they do, there going to say.

I worked for an airline and military discounts are for Active Military only...meaning those enlisted, not their immediate family. The passenger has to show their active military card or a copy of their orders to receive this discount. In most cases, the discount isnt necessarily cheaper and if it is, its not by much.