I would call staples on Tues/Wed before you leave. Just let them know that you want the water delivered on Sat.When you check in let them know you are waiting for a delivery from staples. Staples will deliver from 9am-5pm. When the water arrives, you will receive a phone call from the front desk. Since you are checking in later, I am sure the water will be already waiting for you at the front desk.
We just did this last week and it was wonderful. WOW we saved a bundle!!!!