That must be a huge Waystation. You only need 10 stems of milkweed and probably about that many of nectar plants to certified.
I just wrote a state park an easy way to create a Waystation.
I have a very easy way to plant plants. Lay out the garden by placing the plants that you want to plant. Then, all you do is dig a hole and put the plant in, add a bit of compost and mix it with the existing soil. Once all the plants are planted, then take 4 or more sheets of black and white newspaper, stack those and wet them, then place those near the plants (wetting the newspaper helps to keep it down while you add the mulch) and all grassy areas in the planting bed, add 3 inches of hardwood mulch to the top of that. This will kill/compost the grass. No tilling or digging up the grass. Your garden is done. If you add a plastic/wooden border/edge, this will keep the grass from creeping back in. I usually edge the bed (dig a small trench, too). It's called 'Lasagna Gardening'.http://organicgardening.about.com/od/st ... garden.htm
Butterfly & Hummingbird Garden Mix
These are not all natives, but this would be an excellent start.
Some of these will start blooming in the spring and the others will take 2-3 years to mature because they are perennials. These can also be planted in the spring. http://www.ernstseed.com/products/planting-guide/
I would ask Ernst to leave out some of the non natives out of the mix, like the poppies and bachelor's buttons. Add butterfly weed. It is the low orange flowering milkweed.
[This is $50 a pound.]
If you were planting seeds in the bed that I described above. You'd put down the newspaper, add the mulch and then add 2-3 inches of soil. On top of that soil you could add the seeds. When I used to do this with kids, I'd have them walk on top of the seeds to make seed/soil contact and I'd call this the wildflower dance. You could actually design a program and have those attending do the planting. Let the kids sprinkle the seeds and then do the wildflower dance. The kids and their parents could also help prepared the beds. You could do this in the spring so that you would have time to advertise it. Probably mid May would be a good time to plant (when the soil is warmer). After the dance, I usually would come back and add a light dusting of soil on top of the seed and then tamp that down myself. Then there is the issue of keeping it watered. If it doesn't rain, it needs to be watered at least once a week with a light sprinkle. Let the sprinkler run for an hour at least.