Experts and BHG readers answer.
Raised beds sound like a fine way to overcome your problem. Most perennials will do fine in beds no less than 12" deep, deeper if possible, especially for deep-rooted plants such as any of the pea family. For the beds far away from the water spigot, select perennials such as achillea, coreopsis, echinacea, gaillardia, gaura, and add some low water need shrubs - caryopteris, buddleia, lavender etc. I hope that you are able to get these beds made as I'm sure it will add greatly to the enjoyment of the residents.