Thanks to the Valkyries' presence and Sam's help, the Sanctuary survived the first wave of monsters without a problem. Now all that was left was to find a way to transport all of the survivors across the world.
Sam wished he didn't have to go through so much trouble when he already has enough on his plate, but he couldn't just leave them alone while the Valkyries are away fighting the Olympians.
He was forced to choose between leaving them behind and hoping the monsters wouldn't find them, which was already established as impossible, and taking them along with him to the battlefield where they could die from some stray shots or become the enemy's target.
Either way, he simply couldn't afford to split his forces anymore so at some point the survivors' lives would be left to fate.