Dave's Best Limousine, 215-288-1000
The very first time I flew, Dave's took me to the airport (1990 when I flew to where else but Disney World!). From then until I moved out of Philly in 1995, I used Dave's for all of my airport transport except if I got a ride from a friend or family member. I live down the shore now, but if I stay with someone in my old Northeast Philly neighborhood the night before an early morning PHL flight I call Dave's. I've had 100% success and satisfaction with them.
The only type of vehicle I've ever been picked up in (by Dave's) is a large passenger van. If memory serves they seat about 10 passengers, I think. I know it's three per row plus one in the front passenger seat, and I think there are only three rows, so that would be 10. More than enough for your party.
I assume they service Montgomery County but I can't say for sure.