No, you're not off base. Here are a few thoughts on the plan...

First, both Red Cedar and Eastern Redbud are pretty good at volunteering and if you see seedlings I think you should have little trouble encouraging them to grow. I might try trimming the grass around the seedlings enough to allow the seedlings to get plenty of sunlight. I bet you'll eventually have too many of both and will want to remove some.

Second, lawn grasses were probably planted all over your lot. These grasses don't really make nice wildflower meadows or prairies, so you might think about replacing them with some native grasses and wildflowers. You can find lots of advice on removing a lawn and planting a prairie or meadow, but in general you'll want to eliminate the existing grass first, then add the replacements. I would try a small, manageable area first and see how it goes. Native grasses can take a few years to become established so be patient.

Third, adding wildflowers to a lawn, even an unmown lawn, is not always an easy way to get the wildlfowers established. You should probably remove or kill the grass is an area then add the wildflowers. Otherwise the lawn grass will be too tough a competitor and will severely hamper the growth of wildflowers.

I think your plan is great. Good Luck!

where are you in Illinois?