If you go into the MCAT with complete confidence that you have every chance of making it to your target range, go for it. If you don't, pay the 60 dollars, reschedule and wait a few months. If you're taking it in september I'm guessing you aren't applying for med school until at least next year, you have time. Pick a 3-4 month period that you'll have the least outside distractions and use it for MCAT. Check out SN2ed's schedule(s) in the stickies, or make your own schedule.
Its not wrong to retake your MCAT, but I honestly think that it should only happen if you had a bad test day, i.e you got 11's on PS and BS but you got an 7 on verbal even though you were averaging 10 in practices. If your target range was just 30+ for the med school you had your eye on, I think scheduling a retake one month later and spending that month practicing passages and FLs would be well spent, and you could probably shoot past your target range.