Do you have any "Elite" status with your rental agency (eg. National's Emerald Club) where you can go directly to your car? If not, you can also save some time by splitting up when you get to the luggage carousel (Level 2).
Since it is usually 5-10 mins for the bags to arrive, send the driver down to the rental counter (Level 1) to check out the car. The others can do a last minute potty break or keep an eye out at the carousel.
If the timing works out, the bags will be ready at the same time the driver returns with keys and/or rental agreement (varies with agency).
You can then take bags out to curbside (Level 2 - Arrivals) to wait while the driver goes back down to Level 1, across the roadway to parking garage where rentals cars are parked, then find/drive car back around airport to your waiting family.
Or you might just get a porter to schlep the bags on his cart to your car. Figure $10-15 tip depending on the number of bags you have.
HTH, Steve