Certified GKH Gardening Expert
You don't need any grass around your flowers, which are often part of wildflower seed mixes. Unless you mean native grasses such as prairie dropseed. You can research what other flowers and grasses are native to your area and include a few more of those, or just plant the poppies and cornflower. First I would remove the grass that is already there. Lawn grass will compete with the flowers for nutrients and water.
These articles should help: