You can order two sets of lens and they can be easily interchanged in a matter of seconds. The bigger problem is the AVP is really designed for one person, with occasional "guest" usage (only one Apple ID can be associated with the AVP). Having one AVP may work out if one of you seldom use the device, but I recommend having two if the usage is nearly equal.
You could buy one AVP and try it for 14 days and see if it works for you, then either keep it, return it, or buy a second AVP. You would want to order lens immediately since they take a while to arrive and would probably be a "sunk cost" if you decided to return the unit. I don't know what their policy is about returning the lens.