All you need to do is turn off the wireless switch. That will shut down the WIFI card and should disable built-in Bluetooth.
Tell you the truth, no WIFI signal or otherwise is going to mess with the FMC, ADI, HSI, ND, etc. I can tell you that right now. If it did then the FAA and other country's aviation regulation bodies would have never allowed WIFI for use on aircraft. Even though take off and landing is the most critical phase in flight.
There was a great MythBusters episode on this. Granted it's not scientific and peer reviewed and all that rot, it does show that major wirless wattage won't even deviate and ADI or HSI which I find pretty damn impressive.