Melissa: I didn't have enough blue potatoes from my harvest to try mashed potatoes--I just roasted mine with some other varieties. I'll bet kids would love blue mashed potatoes, though!!
I've not ordered from Woodprairie, but do get their newsletter. I've ordered the past few years from www.potatogarden.com (formerly Ronnigers). They have an amazing selection, but you need to order early because they often sell out of most varieties. I usually order in January for shipping in mid-late March.