Continuity mistake: When Preston is receiving the money from the bank, the banker tells him to put his backpack on the desk. Preston does as told and then the shot goes to the banker putting in the combination to the safe. Then the camera goes back to Preston and he is putting the backpack on the desk again.
Other mistake: When Preston's dad starts to back out of the driveway, he abruptly stops to avoid hitting the moving truck, as if it had just recently appeared there. But they've been there for a while. As soon as he stops, he gets out of the car to start complaining, and the truck driver has already been out of the car for a significant amount of time.
Plot hole: It is not money laundering if you give FBI marked bills to the banker and he hands you back the same marked bills. If the banker had handed back unmarked bills, in regards to the check for cash exchange with the kid, then the FBI teller would never have figured out that "Macintosh" was using the marked FBI money. Thus the money would actually have been laundered. The main villain did not actually do any money laundering, only bank robbery.
Other mistake: During the park chase, Preston swipes the backpack from the person that picks it up, and is still being chased by Quigly. He somehow manages to put the backpack on in a span of about 7 seconds. Considering he is pedaling for his life, and the fear of the men catching him, it's unreasonable to assume that he could have done such a feat so quickly.