Ok I have just had a thought, dont know how well you can coordinate your timings into Cardiff but I dont mind doing a couple of runs from the Station to your hotel to get you there, mind you once the car is parked up for the day its parked up. So if you can all make it within an hour or so of each other, I can take 4 at a time to the hotel. It will save you hanging about for taxi's.
I will then go home and park my car, and join you in the hotel.
Anyway if you are arriving mid afternoon let me know