I'm not sure I quite qualify as "technically skilled," but I might guess that you can edit the kids' special outfits while they are wearing those outfits. They should be accessible either through MasterController (click on a kid, select NRaas > MC > Stylist) or a testingcheats trip to CAS (bring up the cheats console with crtl-shift-c, enter "testingcheatsenabled true" without quotes, shift-click on the kid and select Edit in Create a Sim). If MC Stylist doesn't fix the skin, MC > Advanced > Edit in CAS may work.
And if the joyriding outfit is resistant to change, you could try creating a second one and then deleting the original.
