Well, a while ago I asked about transport options from JW to DLR without carseats. Here's what we did on our recent trip.

We brought the car seats. When we realized that we could bring our older daughter's compact booster (she met the limits for it), we decided to bring them. We took the infant bucket for the 5 month old and the booster. They were easily checked using a car seat protective bag I borrowed from a friend.

We took a taxi (van) from the airport to our hotel. With 4 adults, 2 kids and an infant, it was much cheaper than using a shuttle service and faster too. Our driver was great--he asked us when our return flight was and arrived promptly to take us back to the airport. Plenty of room for us and luggage.

I am very glad you had a good time. My family and I always use the Taxi system when going from John Wayne to Disneyland area. It is just so much more convenient and often costs less too.
Glad it worked out for you and yours as well.:)