Yes, you can use a credit card. When we got to our hotel, the driver helped unload the luggage and then I handed him the coupon and paid for the entire round-trip by credit card and tipped in cash for one-way (it is possible you will have a different driver for the return trip). You can put the tip on the credit card too but for some reason, I like to handout cash for the tip.
We were very satisfied with Tiffany Towncar.