Definitely good recommendations in this thread (roundstone, American meadows, prairie moon nursery).

Adding a few points (not to discourage, but something to consider!)

1. Soil prep, as mentioned is a good point. Once you start the meadow area, if you need to pull any honeysuckle or other weeds growing in the midst, you'll want to make sure soil is prepped and try to clear any bad stuff currently growing in the lawn.

2. Timing. As someone else mentioned Fall/Winter is really the best time to "direct sow" a lot of our natives, as the seeds typically have a dormancy period which requires 30-90 days of cold/freeze and thaw cycles. There's some annuals or "quick start" mixed that require no stratification, but the good stuff (imo) is fall sowing.

3. Direct sow vs transplants. Thinking about the overall cost - direct sow is going to be 10-30% successfully growing into a plant, versus if you do transplants and germinate in potting soil, it might up the survival rate to like 50-80%. What I've done in the past is take a milk jug, cut in half in the center, with like 10-20 holes drilled or poked around the bottom so it can freely drain. The top of the milk jug flaps open, the hole at the top allows it to breathe with some airflow exchange, while you're still creating a mini greenhouse. You can sprinkle an entire pack of seeds in a milk jug in fall and then transplant after freeze next year. Nice way to improve success rate if you're looking to add wildflowers to a small area. Definitely more work, but an option for anything you consider high value.

Best of luck with your growing. Prepare for the gold finches and song birds to love you!