Does McDonalds keep a record of every MAC address? No! MsDonalds ISP does!
Using an untraceable second hand laptop will work….until you visit your email account or attempt to contact your friends with it. Or when the machine with the invisible MAC address is always used where your iPhone is - travels with the iPhone in fact.
Then of course there is the little matter of your Ozrunways running on your iPad…. If it is accessing the Bom, Naips or the Ozrunways traffic server then "ping".