Depending on where you are located you might want to choose a different kind of milkweed. One that doesn't run underground. For example, swamp milkweed, butterfly weed, or you could plant seeds of the tropical milkweed, which grows really fast in the summer.
Here is the Monarch Watch photo guide.
Later you could register your plot as a Waystation.
Monarch Teacher Network
http://www.eirc.org/website/Programs-+a ... twork.html
Major concern is handling the milkweed and getting the sap in your eyes. It can cause a chemical burn. Flush with water at least 20 minutes if this happens.
This website talks about the toxicity.
Common milkweed runs here and there, but it can easily be pulled up when it grows where it is not wanted.