Once you feel they're settled in, if you find that they never use the bottom half of the cage, you might decide to move the food dishes.
I find that keeping my bird's seeds at the bottom of the cage, helps them become familiar with and utilise all the space. Obviously, the lower down they are in the cage, the more risk of poop additions. You can avoid this by making sure that there isn't a perch directly above or using dishes that are covered or if you had one of your little wire platforms above it, you could place a plate/dish there to shelter the food below. Some members who don't use a grate, give the daily (or 1/2 twice daily) seed allowance on fresh papers on the floor of the cage.