If you really want to pass with no worries, get some clean urine from a friend or buy a synthenic urine. Go to your local head shop or google online for Quick Fix or something of that nature. You're right you don't want to dillute, but if you are going to do this naturally, that may be your only option. Keeping up the vitamins and drinking water/gatorade should help. But if you said 2 weeks ago that weekend, I believe you should be okay.