My first thought was contract it out to private companies, but then I remembered that the airrport concession contracts have been a source of mayoral retirement funds here in Atlanta for 40 years.
They are already contracted out.
If you read as far as the second paragraph of the story then you would see that they are employed by a private firm contracted out by the Smithsonian to handle things like concessions and gift shops.
Reading further, the allegation is that the vendor is paying less than the minimum wage and not paying overtime that is accrued. I think that it's fair to insist that the Smithsonian investigate, which they seem to be doing. And if those complaints are true then the Smithsonian should cancel the contract and award it to another company that isn't going to rob its employees.