as reguards to the layout, the time line would work best, the way i thought of is by date registered, as im sure you already have a full list of all the members attending, if not one can be organised then on the look book it states date first registered and organise them simples. then create a layout and have numbered parking slots to which each person gets assigned.
at least this way it will be complete random selection of colours/models/rs/non rs