honestly, i would just start over with Camry OEM sized wheels. steel wheels are fairly inexpensive, and the simplicity of just bolting the wheels on would be a plus.
dealing with spacers and hubcentric rings is rather annoying IMO, not to mention the potential for vibration problems are much worse.
however, if you did not want to spend that much (new wheels, dismounting/mounting tires, that stuff adds up!) i would at the minimum get hubcentric spacers. they will eliminate most vibration problems that can occur with mounting a different sized center bore wheel on the camry.
you can get hubcentric rings from:
I can't say for sure whether or not you need spacers for the offset, but 4 mm doesn't seem like a huge difference. you might be ok without them. easiest way to check is to test fit the mazda winter wheels on the camry!