Tim,
If their cars will fit in your cooking space, they will be able to park in the area. If not, they can park in the front of the cooking area on Friday, but will need to move to the 10 lane boat ramp on Saturday morning about 7 am.
Remember, there will be no traffic allowed in or out of the event from 8 am until about 6 pm, so please plan accordingly. If you think you will need to leave to get supplies from the store or something, please plan to park in the designated parking areas.
Hope this helps.
Thanks,