I assume you have checked all the other local ski shops and rental places in the area? Look in the yellow pages and see what is out there.
Also call Hidden Valley and see what their situation is, maybe you can rent in advance with a credit card. Check on the computer for the rental places near Somerset and Donegal PA.
Lastly, think about putting the childeren in the Ski Chalet or another shop's children's boot program that allows trade-ins as the kids outgrow their equipment; and you might check Ski Chalet or another shop like Alpine or SkiCenter for used boots you could buy.