The trick is to get the augers in as deep as possible. My DH says that when he was little he helped hold a hose in the hole while his dad turned the auger. They somehow shoved the hose in the sand as well, locally liquefying the sand to help with penetration.
Sand is not a soil type I have ever lived with! Kentucky is mostly rocks and clay, with sand only along riverbanks. However we used hurricane type anchors to secure our first house to the bedrock. It is on piers, with an airy space underneath to avoid moisture trouble in the woods. It survived straight line winds near 100 mph during a bad spring storm several years back, with only hairline cracks to drywall mud. I was home alone with the kids, and could swear we were all going to die. Wind like that in a forest isn't just freight train - it sounds like someone loaded gravel in a 747 and is shooting it at you. The USFS flew in circles around us for 2 days trying to find evidence of a tornado, hoping to harvest the timber.
I pray you all weather this thing safely!