We don't have that large a group, just the 3 of us using the car service because even when it's an extended family trip everyone is arriving at different times. But, Mears has a town car service that is around $160 each way for an SUV (or van in the case of your group).
We like it because we arrive during off times, usually landing shortly before midnight or around 7 in the morning. In either case, it's nice to have a private car that is ready to go when we land. The driver has always been waiting for us at the bottom of the escalator heading down to baggage claim, super friendly, clean vehicles, and fwiw, the gratuity is included in the cost.
If your travel group is splitting the cost the price per person is not bad, either.