Please refer to my latter email with regard to the cost.
For airport transfer to hotel - Thb1000
For Ayuttaya day tour - Thb4800
The price list of Thb3200 is a transfer and return service, meaning one drop off point in Ayuttaya and back to Bangkok. As your itinerary includes several stops, therefore the final charge at Thb4800, inclusive 5 stops for sightseeing.
To maxmise your comfort, i have tentatively reserve a Honda CRV for you. It is much better and comfortable vehicle for your group.