1) Dave is right, some people have to work on Saturday, so Sunday would be a better choice. 2) Van is a better option, compared to train. Dont get me wrong, going to Ayutthaya by train is fun, I did it before when I was an undergrad, but its not convenient at all if you would like to visit many places in one day. Some vans can accommodate up to 15 people, so it wouldnt cost you guys that much. It depends how many places you would like to visit, if its not a lot, then go by train, then rent some bikes, sounds like fun, mind you, it can be tiring though lol. Ayutthaya is not that small if you wanna run around the city by bike!! 3) Any ideas yet which place to visit?