You dont want to take too much of the creatine supps. While theres no upper limit for creatinine levels, going overboard on creatine-loading can result in long periods sitting on the toilet seat.
Keep in mind that there are other sources of creatine (ie red meat, fish).

Doing both the magic potion and the dilution method on the day of the test is not a good idea as it'll increases the chances of sample being overdiluted.