I agree - medicals are valid for one year, criminal clearances for six months (and they should be less than 3 months old when submitted with the application). So postpone the medical and get the criminal clearances requests submitted about 6 weeks before the wedding. There's information on
this page of the US2Canada website that tells you how to get FBI requests expedited. If you don't request that they expedite them, it will be 3-4 months to get them back - otherwise, 3-4 weeks.