Thanks for all the feedback everyone! ^
I tried the Express By Execu Car but it does let you book 5 people even though their web site says you can book 5 people. When I put in 5 people I get an error and get bumped up to the higher fare from a van to luxury SUV. I also called them and the same result w/ their computer. The must have changed the policy from 5 down to 4.
Looks like we are going to use Prime Time Shuttle! This really saves the hassle of a 1 way car rental, and dragging luggage to the LAX rental car lot on the bus late at night with the kids after doing the east cost/west coast haul w/ a connection.